I haven't worked as mechanic since my time in the military (1992 - 2012 ) I retired in 2012. In that amount of time there have been so some many advances in automotive technology that have been introduced. That said, with the added technology there have been added problems. Numerous recalls/manufacturer defects to deal with. I would not be confident if i had to work on modern cars today. I'd pull my hair out trying to figure them out. Thank you for sharing your wealth of automotive repair/service knowledge with us. Most folks pay a small fortune to learn this stuff at vocational schools. 👍
I'm sure your viewers appreciate your dedication. Running a shop and trying to get those vehicles out the door all while filming and imparting your analysis and troubleshooting techniques. Always enjoy these case studies and the effort you put in to revealing the fault. Merry Christmas!
Thanks for this info... I'm a 71 year old woman and have to take my car on tomorrow for "P305F".. now I have tons of info going in and can ask questions!!
Awesome breakdown! I found that following the TSB was not very helpful in diagnosing the complexity of this system. One thing I also noticed is when testing either battery in this system you should unhook them first as I found the auxiliary battery was passing a battery test and giving a reading of 190 cca when tested in vehicle and only 87 cca when removed from the vehicle. Before testing out of vehicle I was led to believe the battery control module was bad, however that was not the case!
This module look some way like a glorified couple of diodes that are joined at their catodes to feed the accesories and each anode is conected to one battery. During crank, main battery goes low (9V probably a bit less) and auxiliary remains at 12.5 so the accesories will prefeeer this path. Bateries CANT see each other directly since the diodes are between them, So they remain isolated and accesories will keep working always on the highest voltage. Trying to figure out how much power electronics you can fit an such small box, could be power mosfets instead, but thats all. Power diodes wont drop more than 0.4V and some of them are able to stay below 0.2V. Unsure for car use really. Good vid man. You really explain everything. Best channel I have seen on tech vids. I want ot thank you the effort of filming because working solo and filming, man, your day most have 48 hours. I hope you can get thing working again for you, because you seriously deserve them. Saludos Amigo
So I guess I need a new DBCM. I'm tired of stopping at a red light or stop sign and as soon as I take my foot off the brake the ac/heat cuts off and the radio/bluetooth shuts off. The ac/heat comes back on but I have to wait for the bluetooth to recycle so that it's functional, but by that time, I'm at another red light 😂 Great work, very useful information sir on both part 1 & 2
Another nice video. I am not an auto mechanic, in fact, I cannot drive because my visual disability but I for sure enjoy your videos. I have been able to help people thanks to the things learned here. Awesome. Merry Christmas. 🎄 happy new Year 👍
This have been yet the best results I’ve reviewed. My 2016 Malibu Limited have the same problem with engine light on but also have the Auto Start/Stop issues. The dealer somewhat replaced the main battery and didn’t fix the problem. Also I have replaced the auxiliary battery. Still the problem it is... So with your video, I can present it to my mechanic and we’ll be able to resolve this once for all.
Good job! Excelente trabajo! No traducire el resto para poder hablar mas directo desde el corazon. Hace tiempo no escuchaba un analisis de un circuito electronica de tanto valor practico. Sin usar terminos complejos ni entrar en detalles innecesarios, usted ha sabido decir lo que hace falta y de forma bien clara. Al final hasta nos ha dado una leccion. Tienes mi like y mi suscripcion. Muchisimas gracias. Tengo un caso bastante parecido y usted a hecho que ya no le tenga miedo. Gracias nuevamante. Tengo un canal, puede visitarlo. Algunos videos tienen traduccion.
Im having a main battery charging issue with a 2014 chevy malibu. In the video and the wiring diagram it shows the charging wire attaching to the starter main wire. It actually hooks into the under hood fuse box which leads back to the 250 Amp mega fuse. It is not connected in with the main starter wire on the dual battery module. Battery module fixed my problem. Thank you for all the technical info. Would have pulled all my hair out without it.
Thank you for taking yourtime and explain with great details how the system works and how to trouble shoot it very much appreciated looking forward to your next one thanks again
The IGBT in the DBCM, “which is nothing more than a high current solid-state switch”, took a crap, which is a common thing among IGBTs. Awesome job Dude, don't stop sharing the knowledge.
Eric, I don't think you can test it how you described. If you have a 4 channel scope, connect as follows: 1- Run/crank 12V feed 2-Cranking switched ground 3-Main battery input 4-Aux battery input. Common ground to the DBCM ground pin. Looking at the switching table in your first video, you see that both batteries are connected to the outgoing fuses KOEO. During crank, the main battery is disconnected from the outgoing fuses. So with key off you will likely have slightly different battery voltages as the main battery has supplied quiescent loads while the aux battery has been isolated. You can apply a reasonable load to each (say 2 headlamp bulbs) and watch the battery voltages on the scope to see that the batteries are actually isolated with key off. Next with KOEO you should see the battery voltages become equal. Applying the load should show a drop at both battery inputs. Next in crank you should see the main battery dip under the high starter load and the aux battery stay up at 12V, as should the run crank (key on) input. If the voltage at both battery inputs falls, either the main battery is remaining connected to the output or the auxiliary battery is weak or has high resistance. The amp clamp on the aux battery cable will prove which of the two you're dealing with. (ie you should not see the aux batt contributing to starter current.
thank you for information is very valuable , I serviced a vehicle that arrived with the same code P305F and at this time we found a faulty auxiliary battery, and this was due to that this is a customer's third vehicle and it has been sitting for about two months without being driven, after battery replacement code never came back.
I had the same problem with the impala 2015 and i did replace the auxi battery thought was defective so then some how on the back from the bcm module point to therminal positve was a small crack and replace it and its works but now with this explanation u did now i understand how its works thanks gran maestro 💯👌
I really need to see part one. Part 2 is very interesting to me. I delt with different electrical systems in the past (I was an Auto, [Truck, small engine with generator, some off road equip] Electrician) before retiring in 2016, but this type of equipment still gets my attention.
Start / stop is an abomination. On the Cruze sold here, IT CANT BE DISABLED. I would never buy a car that has this feature and you cant disable it. Yes, it reduces emitions, and also realibility so you must junk the car sooner than expected to buy another one which of course lets you with lots of pollution, scrap and recycling issues and energy wasted. It is a big lie. You want an eco friendly car, just buy a direct injection small diesel. They are super efficient and last longer.
A thing I have seen here in some Buses is that the gearbox goes to park alone after 30 seconds and once you release the brake, in goes to D again, The really saves some fuel by offloading the engine .... guessing if the start / stop garbage is the best solution. Another thing that make me laugh is people wont relinquish the aircon, or all the connected gadgets ... in the end they waste the same energy. What a fiasco. On the buses I mention, the gearbos going into P allow the engine to move the aircon bettern while iddlying. So in the end you get pretty efficient direct injection engines, tailored to the finest trnasmicions to lower diesel consumption, but now, people ask for Aircon at the buses. Same in the metro, we put a couple of lines with the last technology, super efficient tractions systems ... then every coach runs aircon full blast. So the energy you saved on modern state of the art solid state control for the traction motors, then is wasted on cooling 1500 people in rush hour ... LOL ... love it.
Regret the day I bought this car. Nothing but problems. Feels like a scam from gov/dealer. I have had this code from a month after buying car. I have changed both batteries, changed out modules , alternator no shade tree mechanics ,diagnostic came from major dealership yet still dealing with same code. Told mechanic to stop guessing at my expense. Like to know who thought this ideal up bet they wouldn't want their loved one in.
Love the crayons...my car is currently having this problem. I have replaced the main battery and the check engine light is in. I took my car to the dealer and your right the diagnostic test came back stating dual battery fault. I felt this video was describing my problem to s "T". My auto start remote no longer works. I read in the comment this happens after 5 years. Well, that too is correct..my car just turned 5 yrs old. Wow, GM this is terrible.
Awesome follow-up thanks for sharing this! Would be interesting to see if the aux battery had a current draw during cranking indicating it was not being isolated as designed.
Very thorough and well explained. I like how you explained the logic based section of the circuit. I have that code and hope it's only the aux battery that needs to be replace or a bad connection.
very informational video. i was able to make some sense of the starting and wiring diagram. I have a similar car, no crank no start. if you turn the key to on, lights come on in the dash but when you try to crank it, everything goes off in the dash and no response at all. and then comes back to the similar situation in the on position. i tried to use the wiring diagram to trace the starting system but I have no clue how to read it. your video was very helpful but I wonder if you can do separate video on how the read/interpret the starting and wiring diagram so i can better diagnosis why my car is not starting. thanks
Eric your awesome with your videos very detailed and explained as a dyi mechanic how you remember the different cases you do I bet you have slot of them I won’t be able to remember everything lol keep up the good work when you making new videos I have watched almost all your videos
Perhaps a simple test of the switch over could be : 1. Disconnect the main (primary) battery all together. 2. Turn the ignition switch to the accessories position 3. Check that you still have voltage on the accessories (because both batteries are normally in the circuit and the AUX battery will continue to supply the accessories). 4. Turn the key to the crank position and the accessories should continue to operate because they remained on the aux battery. 5. The starter will not work because the main battery is missing. That would also be an indication that the switch worked and is not stuck with both batteries in the circuit. If both batteries are stuck IN the circuit because the switch did not transfer then some of your starter load will be from the AUX battery as well as the main battery so the AUX battery voltage will drop. Maybe this is the actual cause of the error code (i.e. the switch is not isolating like it should and the AUX battery voltage is dropping to
So - come on - rip the top off that battery control module. Inquiring minds want to know what's in there. I assume because it's so thin it's probably some big honking MOSFETS and some drive circuitry. Maybe you can do a Russian fix on it :-) no parts required.
@@richardcranium5839 I see a potential problem. It might be that disconnecting the main battery may leave the whole car disabled (for some other engineered reason) so you can't even test the theory. I guess you'd need the vehicle present to test whatever theory you come up with. It would be good to come up with some sort of test because as these things go the parts cannon can get expensive.
Amen brother. Exactly what I was thinking. I have gone through auxiliary batteries every 6 months. Only thing I can think of is it's constantly being used , bad switch.
Really really good information I have watched Part 1 and Part 2 and now feel so certain now I know all about this system thanx to your videos. I have had a bi with this problem had already replaced the auxiliary battery but still get the P305f code but once finding your video and learning about the “DBCM” I feel so confident to about that part being the problem even though not doing any testing first just from just gut feeling and your videos but to where when I call the shops looking for them they have no idea what I’m talking about and have to explain to them about the part and it’s function when then they play “oh yea” game! But just wanted to share that with you and again thank you for the clear and thorough videos,
lmao @ the crayons love it!!! i could see monitoring the two voltages with a scope to see if it drops when cranking. and also the sense to see when it goes to ground. that should give a picture. a meter wont be fast enough. i suspect large mosfets inside.
Jake, there's no way...if I had a known bad module...a sealed one...that I wouldn't dremel it open and look inside to see what failed. I don't think I could go to sleep without knowing, as a matter of fact. I'd want to verify that the drop in voltage on the x3 lead caused a relay to energize inside and cause the change in battery being used. Unless the customer wanted the thing back to do so herself, that is. Then I'd be asking her to let me know.
Very useful and informative video. Thank you. Quick question. One of the fuses keeps blowing. The starter and alternator have been replaced. So has the fuse box itself. It takes a couple of days to happen, but it does. Why do you think that is?
Thanks for the info. My daughters Malibu starts fine but she is having issues with accessories shutting off when it goes into eco mode at red lights. Both batteries were tested and deemed good. Wonder if that means replacing DBCM will solve the issue? Thank you for sharing your knowledge my friend.
I have that problem also and the brake light staying on when letting off the pedal it does it when daytime running lights but night time they work like there supposed to I just went to the junk yard yesterday and pulled this whole fuse block and swapped it with mine now the brake lights work like there supposed to when day time running lights are on still haven't had it do the auto stop to see if it fixed the radio. Did you ever get your daughters radio to work right?
@eb6736 , I just started experiencing this same issue today. My radio is shutting off when I come to red lights because of the eco mode. Both batteries were tested to be good. Did you ever change out the DBCM and did that resolve the problem?
We need a part III, take a sledge hammer to the lid on the module, let's look inside. With such high current devices, it doesn't take much resistance to cause a fail. Problem is, simple resistance testing in an active circuit is not as uncomplicated as one would think. They say it can be done with the PP IV, but in my hands some readings don't make sense.
Man that's ridiculous, do we really have a starting problem with cars, just something else to go wrong. Oh well something else for us to make money on. Great job Eric you da man.
Nice part 2 video ,nice crayons.I seen a similar bcm on an opel astra the other day car just needed a new battery. The bcm just looks like a breeding ground for restince.
So I have this exact model and my issue isn’t it throwing a code. In fact there are no codes. But once mine goes into auto stop it stalls out trying to restart the engine. The starter is moving but it gives two attempts before quitting. Usually 2 -3 attempts after the starter turning for some time before it fully starts the engine. Do you think the DBCM could be the issue in my case as well?
Amigo, he vuelto nuevamante a esta segunda parte. Todo me parece muy bien comprendido y explicado, pero, me surgieron algunas dudas. No mencionas y no se ve en el diagrama que muestras el pin 1 del DBCM. Sin embargo estoy viendo en Mitchell que hay un cable yel/blu desde el pin 1 hasta el pin 49 del ECM. Cuando me trajeron el auto me dijeron que habían comprado nuevo la caja de fusible de sobre la batería con el módulo DBCM. Lo primero que le sucedío al auto fué que cojióo candela y derritio esa caja de fusibles y el motor de arranque echó mucho humo. Cambiaron ambas cosas y como no lo lograron arrancar, me lo trajeron. Ahora tengo dudas, porque en el módulo DBCM hay continuidad permanentemente, sin poner el plug fino de los 4 pines de comandos. Mencionas en el video que cuando se pone el sw en ON, debe conectar la batería principal. Y me pregunto, si está abierto antes, de donde saque la corriente para enviarla a los relay y luego al DBCM para hacer esa conección. Lo que me dice que tiene sentido que este Normally Close entre la bateria principal y los accesorios. Luego cuando pasamos a arranque, que abra el contacto de esa bateria y conecte la auxiliar. Luego de estar arrancado, conecta ambas. Cuando apagamos, desconecta la auxiliar, que ha dejado cargada y conecta la grande nuevamante, para incluso dejar las memorias de los modulos, del radio, dejar el sistema de control remoto para los seguros, el arranque remoto etc. Se que hace 4 años que hiciste estos dos buenos videos, pero seguramente has tenido que lidiar con otros y quizás estás actualizado con este problema. Me gustaría mucho que pudieras diciparme esas dudas. No se si los que me antecedieron, en su afán de prenderlo, rompieron tambien el modulo nuevo o si está bueno. Gracias nuevamante. Un saludo amistoso.
@@1662ks the car would shut off at a red light as normal but upon releasing the brake when the engine would restart it would also reboot the radio each time which was a mild annoyance at its least but would also hang up on people when I happened to be on a call. The auto stop start became really rough and obviously lit up the check engine light, my auxiliary battery tested fine so I ended up replacing the fuse block on top of the battery with one from ebay for $50 and about 30 minutes of time with a few hand tools, everything works perfect now, good as new
chase vogt do you have the link to the part? I actually just purchased a 2015 Malibu and while I haven’t received a check engine light or a complete shut down, upon releasing the brake, I do get dimmed lights as well as the radio reboot. Also the battery voltage drops down to about 12.1
Kenneth Sullivan www.ebay.com/itm/NEW-GM-Fuse-Distribution-Block-23223079-For-2010-15-ATS-Impala-Malibu-Regal-/233282063829 That’s the one that I bought for my 2015 Chevy Malibu 2.5L or you can search for “2015 Chevy Malibu Battery Fuse Block” the same part is used in multiple GM vehicle including the a Buick Regal let me know if you need anything else more than happy to help
Kenneth Sullivan also here is a link to a forum post where us Malibu owners spoke about the topic www.chevymalibuforum.com/threads/p305f-check-engine-code.106833/page-2
I'm guessing the "ignition voltage input" on the codes setting criteria is referring to the general "vehicle wide" ignition voltage, which should be switched to the aux battery during cranking. The computer was detecting the voltage drop when the starter was engaged because the aux battery was not being switched in (or main not being switched out).
I hope you can help me out with this question. After you swap out the Dual battery control module do you have to do any kind of Programming??? Or is a quick clear codes and we good to go.
I was wondering after you install the new Dual Battery Control Module do you have to get a relearn done on it or program it at all, or will it work without doing that? I have a 2015 chevy impala with the same P0305F code and I did the process of elimination from getting a new aux battery, checking the main battery, looking for loose grounds and or pinched wires underneath the battery tray. I just bought the new DBCM and i am curious if i need to get a relearn done on it after i install it ?
I have the same question. Do you have reprogram anything after you swap it out? Like the dealer said it has to be reprogrammed but idk if it’s bullshit or what
Your smart and I appreciate you!! I wish you were here right now to help with my 2015 Malibu lol..my check engine light goes off and on with this code for 8 months. Aux battery says it has 12 volts. I probably just need to change the dang computer. But in the meantime it runs great but all the sudden started smelling like rotten eggs..I know cat right?? Maybe?? But that also comes and goes in the last couple days. Just changed the spark plugs yesterday seemed good and no smell until I drove for 6 hours(Lyft driver) then smell came back but sewage instead smh. And then goes away again.131,000 miles. No check engine light on for weeks. Battery cables look clean..I'm just a girl without training and never want to believe what mechanics says cause the ones I have had lie. And yes I know there are amazing honest ones out there just can't seem to find them. Ugh I spend more time trying look this shit up and figure it out with guys like you. Just wanted to say thank you for your time and teaching skills!!! Heck I will probably find out it's a gas cap making sewage smell possible 🤣😡 love my Malibu 😪
Auto stop reads the primary battery and not the aux battery whenever, the vehicle stops. The same sheet that you shown in part one. My vehicle is showing p305f code. Before that it was just reading the aux battery code. Should, I follow your video and do the same checks or do something different?
It also switches accessories to the aux battery to prevent voltage drops/spikes to accessories and modules while cranking. Systems like these expose the guys around you that have a lack of knowledge of electrical systems. We had one of these come in that had a blown fuse to the Aux battery due to someone messing around with the connections. It took me thirty minutes to get a guy to understand why there was voltage on both sides of the fuse even though it was blown 😂. He just couldn’t grasp that the alternator was on one side of the blown fuse and a low battery on the other side of the fuse. I try to teach guys while helping them work through a problem but the ones that constantly come for help for the same things and never learn I just take over the job from and they usually don’t last too long. It seems like our industry is full of guys like that. They think electricity is some kind of magical thing they can’t learn when in reality it’s much simpler than they want to believe it is. It’s like they can’t grasp anything because they’ve already psyched themselves out into believing it’s above their heads before you even tell them anything. It drives me nuts.
I replace the alternator on my 2014 Chevy Malibu and it worked for a week and then it started with the same thing that it wouldn’t start it’s got 42,000 miles on it with original battery is it more likely to be the battery or the dual battery control module
My main battery isnt charging but back one is..i get 14 volts when started across the whole fuse deal..but only 12 volts at the battery...and battery dies fast..help!!
Great explanation Eric do u think the way we think of explaining electron direction and flow will change meaning electron direction is neg to positive and current FLOW IS FROM POSITIVE TO NEGATIVE. Yes no ? You do a great job of breaking down a schematic
I haven't worked as mechanic since my time in the military (1992 - 2012 ) I retired in 2012. In that amount of time there have been so some many advances in automotive technology that have been introduced.
That said, with the added technology there have been added problems. Numerous recalls/manufacturer defects to deal with. I would not be confident if i had to work on modern cars today. I'd pull my hair out trying to figure them out.
Thank you for sharing your wealth of automotive repair/service knowledge with us. Most folks pay a small fortune to learn this stuff at vocational schools. 👍
Nice to hear from a diagnostic technician, not a parts changer. I love your methods, and love your skills.
Eric is an excellent teacher. He explains things in detail in a very understandable way. Keep them coming Eric!
I second that 💪🏼. Wish he was my neighbor 🤣
I'm sure your viewers appreciate your dedication. Running a shop and trying to get those vehicles out the door all while filming and imparting your analysis and troubleshooting techniques. Always enjoy these case studies and the effort you put in to revealing the fault. Merry Christmas!
Thanks for this info... I'm a 71 year old woman and have to take my car on tomorrow for "P305F".. now I have tons of info going in and can ask questions!!
Awesome breakdown! I found that following the TSB was not very helpful in diagnosing the complexity of this system. One thing I also noticed is when testing either battery in this system you should unhook them first as I found the auxiliary battery was passing a battery test and giving a reading of 190 cca when tested in vehicle and only 87 cca when removed from the vehicle. Before testing out of vehicle I was led to believe the battery control module was bad, however that was not the case!
This module look some way like a glorified couple of diodes that are joined at their catodes to feed the accesories and each anode is conected to one battery. During crank, main battery goes low (9V probably a bit less) and auxiliary remains at 12.5 so the accesories will prefeeer this path. Bateries CANT see each other directly since the diodes are between them, So they remain isolated and accesories will keep working always on the highest voltage. Trying to figure out how much power electronics you can fit an such small box, could be power mosfets instead, but thats all. Power diodes wont drop more than 0.4V and some of them are able to stay below 0.2V. Unsure for car use really. Good vid man. You really explain everything. Best channel I have seen on tech vids. I want ot thank you the effort of filming because working solo and filming, man, your day most have 48 hours. I hope you can get thing working again for you, because you seriously deserve them. Saludos Amigo
Much respect to you for taking the time to give more information about the module
So I guess I need a new DBCM. I'm tired of stopping at a red light or stop sign and as soon as I take my foot off the brake the ac/heat cuts off and the radio/bluetooth shuts off. The ac/heat comes back on but I have to wait for the bluetooth to recycle so that it's functional, but by that time, I'm at another red light 😂 Great work, very useful information sir on both part 1 & 2
I have the same problem and found that putting it in neutral helps with that
Another nice video. I am not an auto mechanic, in fact, I cannot drive because my visual disability but I for sure enjoy your videos. I have been able to help people thanks to the things learned here. Awesome. Merry Christmas. 🎄 happy new Year 👍
Awesome job! Thank you so much for sharing your knowledge! Not a car mechanic. So everything helps!
This have been yet the best results I’ve reviewed. My 2016 Malibu Limited have the same problem with engine light on but also have the Auto Start/Stop issues. The dealer somewhat replaced the main battery and didn’t fix the problem. Also I have replaced the auxiliary battery. Still the problem it is... So with your video, I can present it to my mechanic and we’ll be able to resolve this once for all.
Did the video make it work ? Do you still have a check engine light ?
@@darneshiaelder2102 Yes it did work. Check engine light went off. $200 for part though. 45 minutes to change it out for new one.
Glad to see this worked, I have the same car and both batteries are new/ have been checked. Looks like I may finally know what needs to be changed.
Good job! Excelente trabajo! No traducire el resto para poder hablar mas directo desde el corazon. Hace tiempo no escuchaba un analisis de un circuito electronica de tanto valor practico. Sin usar terminos complejos ni entrar en detalles innecesarios, usted ha sabido decir lo que hace falta y de forma bien clara. Al final hasta nos ha dado una leccion. Tienes mi like y mi suscripcion. Muchisimas gracias. Tengo un caso bastante parecido y usted a hecho que ya no le tenga miedo. Gracias nuevamante. Tengo un canal, puede visitarlo. Algunos videos tienen traduccion.
Im having a main battery charging issue with a 2014 chevy malibu. In the video and the wiring diagram it shows the charging wire attaching to the starter main wire. It actually hooks into the under hood fuse box which leads back to the 250 Amp mega fuse. It is not connected in with the main starter wire on the dual battery module. Battery module fixed my problem. Thank you for all the technical info. Would have pulled all my hair out without it.
Thank you for taking yourtime and explain with great details how the system works and how to trouble shoot it very much appreciated looking forward to your next one thanks again
The IGBT in the DBCM, “which is nothing more than a high current solid-state switch”, took a crap, which is a common thing among IGBTs. Awesome job Dude, don't stop sharing the knowledge.
Eric, I don't think you can test it how you described.
If you have a 4 channel scope, connect as follows:
1- Run/crank 12V feed
2-Cranking switched ground
3-Main battery input
4-Aux battery input.
Common ground to the DBCM ground pin.
Looking at the switching table in your first video, you see that both batteries are connected to the outgoing fuses KOEO.
During crank, the main battery is disconnected from the outgoing fuses.
So with key off you will likely have slightly different battery voltages as the main battery has supplied quiescent loads while the aux battery has been isolated.
You can apply a reasonable load to each (say 2 headlamp bulbs) and watch the battery voltages on the scope to see that the batteries are actually isolated with key off.
Next with KOEO you should see the battery voltages become equal.
Applying the load should show a drop at both battery inputs.
Next in crank you should see the main battery dip under the high starter load and the aux battery stay up at 12V, as should the run crank (key on) input.
If the voltage at both battery inputs falls, either the main battery is remaining connected to the output or the auxiliary battery is weak or has high resistance. The amp clamp on the aux battery cable will prove which of the two you're dealing with. (ie you should not see the aux batt contributing to starter current.
thank you for information is very valuable , I serviced a vehicle that arrived with the same code P305F and at this time we found a faulty auxiliary battery, and this was due to that this is a customer's third vehicle and it has been sitting for about two months without being driven, after battery replacement code never came back.
I had the same problem with the impala 2015 and i did replace the auxi battery thought was defective so then some how on the back from the bcm module point to therminal positve was a small crack and replace it and its works but now with this explanation u did now i understand how its works thanks gran maestro 💯👌
I really need to see part one. Part 2 is very interesting to me. I delt with different electrical systems in the past (I was an Auto, [Truck, small engine with generator, some off road equip] Electrician) before retiring in 2016, but this type of equipment still gets my attention.
Incredible amount of complexity and expense added by manufacturers and government to save pennies of gas to stop and restart engines at a stop sign.
i'm curious how the starters and everything else will hold up. cant imagine city stop light to stoplight operation.
Start / stop is an abomination. On the Cruze sold here, IT CANT BE DISABLED. I would never buy a car that has this feature and you cant disable it. Yes, it reduces emitions, and also realibility so you must junk the car sooner than expected to buy another one which of course lets you with lots of pollution, scrap and recycling issues and energy wasted. It is a big lie. You want an eco friendly car, just buy a direct injection small diesel. They are super efficient and last longer.
A thing I have seen here in some Buses is that the gearbox goes to park alone after 30 seconds and once you release the brake, in goes to D again, The really saves some fuel by offloading the engine .... guessing if the start / stop garbage is the best solution. Another thing that make me laugh is people wont relinquish the aircon, or all the connected gadgets ... in the end they waste the same energy. What a fiasco. On the buses I mention, the gearbos going into P allow the engine to move the aircon bettern while iddlying. So in the end you get pretty efficient direct injection engines, tailored to the finest trnasmicions to lower diesel consumption, but now, people ask for Aircon at the buses. Same in the metro, we put a couple of lines with the last technology, super efficient tractions systems ... then every coach runs aircon full blast. So the energy you saved on modern state of the art solid state control for the traction motors, then is wasted on cooling 1500 people in rush hour ... LOL ... love it.
You can disable it by wiring out this module but the engine service light will light.
Regret the day I bought this car. Nothing but problems. Feels like a scam from gov/dealer. I have had this code from a month after buying car. I have changed both batteries, changed out modules , alternator no shade tree mechanics ,diagnostic came from major dealership yet still dealing with same code. Told mechanic to stop guessing at my expense. Like to know who thought this ideal up bet they wouldn't want their loved one in.
Love the crayons...my car is currently having this problem. I have replaced the main battery and the check engine light is in. I took my car to the dealer and your right the diagnostic test came back stating dual battery fault. I felt this video was describing my problem to s "T". My auto start remote no longer works. I read in the comment this happens after 5 years. Well, that too is correct..my car just turned 5 yrs old. Wow, GM this is terrible.
You sir, are a professional. Your explanation are on point!
This was very helpful. Thank you for taking me through the steps. You can work on my car anytime :)
Excellent video. I have a 2015 Malibu. This will be a big help when mine sets this code
Thanks for making this video. Troubleshooting my 2016 Malibu
This video was very helpful 👏 👌. This was the problem. Recommended
Awesome follow-up thanks for sharing this! Would be interesting to see if the aux battery had a current draw during cranking indicating it was not being isolated as designed.
Excellent way u explain and very easy to understand how this dual batt circuit works. Keep those very educative videos.
Thanks for the detailed explanation! Just earned yourself a new subscriber!
Eric, Thanks for explaining this control module,nice job. Charlie
Thanks for the detailed explanation! Great video as always!
Very good video. This should be helpful to many. A search for trouble shooting a DBCM on the internet leads you to it.
You have been a great help.Thank you so much. Best video yet!!
Thanks so much I’m dealing with headlight draw dimming. Rn can’t figure out I been checking these all wires
Thanks, good training, very good illustration.
Very thorough and well explained. I like how you explained the logic based section of the circuit. I have that code and hope it's only the aux battery that needs to be replace or a bad connection.
very informational video. i was able to make some sense of the starting and wiring diagram. I have a similar car, no crank no start. if you turn the key to on, lights come on in the dash but when you try to crank it, everything goes off in the dash and no response at all. and then comes back to the similar situation in the on position. i tried to use the wiring diagram to trace the starting system but I have no clue how to read it. your video was very helpful but I wonder if you can do separate video on how the read/interpret the starting and wiring diagram so i can better diagnosis why my car is not starting. thanks
Nice explation ..... Was waiting for 2nd part .... Thanks for sharing this valuable information
Eric your awesome with your videos very detailed and explained as a dyi mechanic how you remember the different cases you do I bet you have slot of them I won’t be able to remember everything lol keep up the good work when you making new videos I have watched almost all your videos
Saludos Eric excelente explicacion eres todo un profesional me sirvio de mucho tu explicacion felicidades!👌👍😎
Perhaps a simple test of the switch over could be :
1. Disconnect the main (primary) battery all together.
2. Turn the ignition switch to the accessories position
3. Check that you still have voltage on the accessories (because both batteries are normally in the circuit and the AUX battery will continue to supply the accessories).
4. Turn the key to the crank position and the accessories should continue to operate because they remained on the aux battery.
5. The starter will not work because the main battery is missing. That would also be an indication that the switch worked and is not stuck with both batteries in the circuit.
If both batteries are stuck IN the circuit because the switch did not transfer then some of your starter load will be from the AUX battery as well as the main battery so the AUX battery voltage will drop. Maybe this is the actual cause of the error code (i.e. the switch is not isolating like it should and the AUX battery voltage is dropping to
So - come on - rip the top off that battery control module. Inquiring minds want to know what's in there. I assume because it's so thin it's probably some big honking MOSFETS and some drive circuitry. Maybe you can do a Russian fix on it :-) no parts required.
i see your thought process. add in voltage drop testing and ya may have it
@@richardcranium5839 I see a potential problem. It might be that disconnecting the main battery may leave the whole car disabled (for some other engineered reason) so you can't even test the theory. I guess you'd need the vehicle present to test whatever theory you come up with. It would be good to come up with some sort of test because as these things go the parts cannon can get expensive.
Amen brother. Exactly what I was thinking. I have gone through auxiliary batteries every 6 months. Only thing I can think of is it's constantly being used , bad switch.
Really really good information I have watched Part 1 and Part 2 and now feel so certain now I know all about this system thanx to your videos. I have had a bi with this problem had already replaced the auxiliary battery but still get the P305f code but once finding your video and learning about the “DBCM” I feel so confident to about that part being the problem
even though not doing any testing first just from just gut feeling and your videos but to where when I call the shops looking for them they have no idea what I’m talking about and have to explain to them about the part and it’s function when then they play “oh yea” game! But just wanted to share that with you and again thank you for the clear and thorough videos,
Amazing video. Thank you for the in depth analysis.
lmao @ the crayons love it!!! i could see monitoring the two voltages with a scope to see if it drops when cranking. and also the sense to see when it goes to ground. that should give a picture. a meter wont be fast enough. i suspect large mosfets inside.
Jake, there's no way...if I had a known bad module...a sealed one...that I wouldn't dremel it open and look inside to see what failed. I don't think I could go to sleep without knowing, as a matter of fact. I'd want to verify that the drop in voltage on the x3 lead caused a relay to energize inside and cause the change in battery being used. Unless the customer wanted the thing back to do so herself, that is. Then I'd be asking her to let me know.
Very well explained!!! Awesome job!!!
Very useful and informative video. Thank you. Quick question. One of the fuses keeps blowing. The starter and alternator have been replaced. So has the fuse box itself. It takes a couple of days to happen, but it does. Why do you think that is?
Thanks for the info. My daughters Malibu starts fine but she is having issues with accessories shutting off when it goes into eco mode at red lights. Both batteries were tested and deemed good. Wonder if that means replacing DBCM will solve the issue? Thank you for sharing your knowledge my friend.
I have that problem also and the brake light staying on when letting off the pedal it does it when daytime running lights but night time they work like there supposed to I just went to the junk yard yesterday and pulled this whole fuse block and swapped it with mine now the brake lights work like there supposed to when day time running lights are on still haven't had it do the auto stop to see if it fixed the radio. Did you ever get your daughters radio to work right?
@eb6736 , I just started experiencing this same issue today. My radio is shutting off when I come to red lights because of the eco mode. Both batteries were tested to be good. Did you ever change out the DBCM and did that resolve the problem?
@@lettyluuu9778I replaced Both battery, body control module, & cleaned ground. Still not working
We need a part III, take a sledge hammer to the lid on the module, let's look inside. With such high current devices, it doesn't take much resistance to cause a fail. Problem is, simple resistance testing in an active circuit is not as uncomplicated as one would think. They say it can be done with the PP IV, but in my hands some readings don't make sense.
Man that's ridiculous, do we really have a starting problem with cars, just something else to go wrong. Oh well something else for us to make money on. Great job Eric you da man.
Thanks for that 100% Completely explanation.
Your friend from Reynosa Mexico
Bronco
Great video thanks for sharing your knowledge
Your a very clever man , manny thanks for a great video with you explaining it 👍👍😀
Does the dual-battery module have to be programmed once it's installed or is it plug & Play
Amazing explanation thanks alot❤👍👍👍
Nice part 2 video ,nice crayons.I seen a similar bcm on an opel astra the other day car just needed a new battery. The bcm just looks like a breeding ground for restince.
So I have this exact model and my issue isn’t it throwing a code. In fact there are no codes. But once mine goes into auto stop it stalls out trying to restart the engine. The starter is moving but it gives two attempts before quitting. Usually 2 -3 attempts after the starter turning for some time before it fully starts the engine. Do you think the DBCM could be the issue in my case as well?
Very good rundown on the dbcm. Thank you and Merry Christmas. Cheers.
Amigo, he vuelto nuevamante a esta segunda parte. Todo me parece muy bien comprendido y explicado, pero, me surgieron algunas dudas. No mencionas y no se ve en el diagrama que muestras el pin 1 del DBCM. Sin embargo estoy viendo en Mitchell que hay un cable yel/blu desde el pin 1 hasta el pin 49 del ECM. Cuando me trajeron el auto me dijeron que habían comprado nuevo la caja de fusible de sobre la batería con el módulo DBCM. Lo primero que le sucedío al auto fué que cojióo candela y derritio esa caja de fusibles y el motor de arranque echó mucho humo. Cambiaron ambas cosas y como no lo lograron arrancar, me lo trajeron. Ahora tengo dudas, porque en el módulo DBCM hay continuidad permanentemente, sin poner el plug fino de los 4 pines de comandos. Mencionas en el video que cuando se pone el sw en ON, debe conectar la batería principal. Y me pregunto, si está abierto antes, de donde saque la corriente para enviarla a los relay y luego al DBCM para hacer esa conección. Lo que me dice que tiene sentido que este Normally Close entre la bateria principal y los accesorios. Luego cuando pasamos a arranque, que abra el contacto de esa bateria y conecte la auxiliar. Luego de estar arrancado, conecta ambas. Cuando apagamos, desconecta la auxiliar, que ha dejado cargada y conecta la grande nuevamante, para incluso dejar las memorias de los modulos, del radio, dejar el sistema de control remoto para los seguros, el arranque remoto etc.
Se que hace 4 años que hiciste estos dos buenos videos, pero seguramente has tenido que lidiar con otros y quizás estás actualizado con este problema. Me gustaría mucho que pudieras diciparme esas dudas. No se si los que me antecedieron, en su afán de prenderlo, rompieron tambien el modulo nuevo o si está bueno.
Gracias nuevamante. Un saludo amistoso.
Nice video bro. Thanks, that explains a lot actually.
Eric thank you for answering my question four weeks ago appreciate
What can I say but great video! you sure know how to explain your theory (know-how), again Thanks.
Right on thank you man I just replaced my battery fuse block and it fixed my problem I got it on eBay for $50
chase vogt what exactly was your problem
@@1662ks the car would shut off at a red light as normal but upon releasing the brake when the engine would restart it would also reboot the radio each time which was a mild annoyance at its least but would also hang up on people when I happened to be on a call.
The auto stop start became really rough and obviously lit up the check engine light, my auxiliary battery tested fine so I ended up replacing the fuse block on top of the battery with one from ebay for $50 and about 30 minutes of time with a few hand tools, everything works perfect now, good as new
chase vogt do you have the link to the part? I actually just purchased a 2015 Malibu and while I haven’t received a check engine light or a complete shut down, upon releasing the brake, I do get dimmed lights as well as the radio reboot. Also the battery voltage drops down to about 12.1
Kenneth Sullivan www.ebay.com/itm/NEW-GM-Fuse-Distribution-Block-23223079-For-2010-15-ATS-Impala-Malibu-Regal-/233282063829
That’s the one that I bought for my 2015 Chevy Malibu 2.5L or you can search for “2015 Chevy Malibu Battery Fuse Block” the same part is used in multiple GM vehicle including the a Buick Regal let me know if you need anything else more than happy to help
Kenneth Sullivan also here is a link to a forum post where us Malibu owners spoke about the topic www.chevymalibuforum.com/threads/p305f-check-engine-code.106833/page-2
If my pscm is missing can that be what’s causing it to drain my battery
How do i check fuses in the module with my multimeter
Man that was a great break down on that unit, keep up the content
I'm guessing the "ignition voltage input" on the codes setting criteria is referring to the general "vehicle wide" ignition voltage, which should be switched to the aux battery during cranking. The computer was detecting the voltage drop when the starter was engaged because the aux battery was not being switched in (or main not being switched out).
So you can bypass that starter fues?to start it on a emergency?by jumping positive to starter post?
Thanks brother'Great Info ecplained well👍
I hope you can help me out with this question. After you swap out the Dual battery control module do you have to do any kind of Programming??? Or is a quick clear codes and we good to go.
I was wondering after you install the new Dual Battery Control Module do you have to get a relearn done on it or program it at all, or will it work without doing that? I have a 2015 chevy impala with the same P0305F code and I did the process of elimination from getting a new aux battery, checking the main battery, looking for loose grounds and or pinched wires underneath the battery tray. I just bought the new DBCM and i am curious if i need to get a relearn done on it after i install it ?
I have the same question. Do you have reprogram anything after you swap it out? Like the dealer said it has to be reprogrammed but idk if it’s bullshit or what
You may want check the idle load on axillary battery. If it is low that may trigger the system to not work properly and set the check enigine light.
NICE!!! I WAS WAITING FOR THIS VIDEO. NICE WAY END THE NIGHT. THANK YOU
Thanks for your useful info I was waiting for this video
Your smart and I appreciate you!! I wish you were here right now to help with my 2015 Malibu lol..my check engine light goes off and on with this code for 8 months. Aux battery says it has 12 volts. I probably just need to change the dang computer. But in the meantime it runs great but all the sudden started smelling like rotten eggs..I know cat right?? Maybe?? But that also comes and goes in the last couple days. Just changed the spark plugs yesterday seemed good and no smell until I drove for 6 hours(Lyft driver) then smell came back but sewage instead smh. And then goes away again.131,000 miles. No check engine light on for weeks. Battery cables look clean..I'm just a girl without training and never want to believe what mechanics says cause the ones I have had lie. And yes I know there are amazing honest ones out there just can't seem to find them. Ugh I spend more time trying look this shit up and figure it out with guys like you. Just wanted to say thank you for your time and teaching skills!!! Heck I will probably find out it's a gas cap making sewage smell possible 🤣😡 love my Malibu 😪
Awesome info and explanation! 👍
where do you get that dual battery control module
I hope you can answer this question for me does that module habe to be programed or will the ecm burn the vin into it by itself like a tipm
Exceptional ...thank you !
So A a bad DBCM could cause no starting issue ? or the auxiliary battery could be the culprit?
Really good info, thank you
Does it affect the performance of the transmission when you put it on gear?
Auto stop reads the primary battery and not the aux battery whenever, the vehicle stops. The same sheet that you shown in part one. My vehicle is showing p305f code. Before that it was just reading the aux battery code. Should, I follow your video and do the same checks or do something different?
Excellent video Eric and Merry Christmas to you and family. ❤️
It also switches accessories to the aux battery to prevent voltage drops/spikes to accessories and modules while cranking. Systems like these expose the guys around you that have a lack of knowledge of electrical systems. We had one of these come in that had a blown fuse to the Aux battery due to someone messing around with the connections. It took me thirty minutes to get a guy to understand why there was voltage on both sides of the fuse even though it was blown 😂. He just couldn’t grasp that the alternator was on one side of the blown fuse and a low battery on the other side of the fuse. I try to teach guys while helping them work through a problem but the ones that constantly come for help for the same things and never learn I just take over the job from and they usually don’t last too long. It seems like our industry is full of guys like that. They think electricity is some kind of magical thing they can’t learn when in reality it’s much simpler than they want to believe it is. It’s like they can’t grasp anything because they’ve already psyched themselves out into believing it’s above their heads before you even tell them anything. It drives me nuts.
Just tell them to go do a brake job and leave the electrical work to the expert 😁
How did you know the fuse was blown?😁
Has the customer returned with the same issue after you installed the assembly in part 1 or did the new install fix the problem?
I replace the alternator on my 2014 Chevy Malibu and it worked for a week and then it started with the same thing that it wouldn’t start it’s got 42,000 miles on it with original battery is it more likely to be the battery or the dual battery control module
Question if a starter motor is going bad would it cause the P305F to fault?
Good video, I found it informative n educational
I got the code P305F, is it the aux battery from the trunk? Or is it the entire module?
Being that it’s a module. Did you have to program it? And if so did you use a pass thru?
@advanced level auto is there anything special I gotta do to change this?
Great explanation !!
It’s very entertaining thanks 🙏
My main battery isnt charging but back one is..i get 14 volts when started across the whole fuse deal..but only 12 volts at the battery...and battery dies fast..help!!
Great explanation Eric do u think the way we think of explaining electron direction and flow will change meaning electron direction is neg to positive and current FLOW IS FROM POSITIVE TO NEGATIVE. Yes no ? You do a great job of breaking down a schematic
I have the same issue. Replaced aux battery and same code p305f. No luck in fixing
I need to get a new dual battery control module for my 2015 Chevy Malibu but i don’t know where to order it from. Any idea of where i can order one?
So if this part goes out will it effect my auto stop/star?