That was cool, Jake! Now if this was a European car, it would tell you on the message center exactly which bulb was burnt out... Because Euro cars are superior to all other cars 😆
I was a young mechanic working in NW Pennsylvania in 1986 when the "third brake light" was first required on all vehicles and being certified to do inspections I knew it as a collision avoidance light. Thank you for another video with invaluable information. You are the best!
I always wondered if the manufactures go back and revise their wiring diagrams after finding out how many good techs have been misled by this kind of stuff. Thanks so much for educating us Jake!
I had a similar experience with a Subaru, which locked itself in park when the rear right brake light fuse was blown. I had put an incorrect replacement bulb in for a blown bulb, and it blew the circuit fuse, and that prompted the car to lock itself in park for safety. The diagnosis was easy because I knew what I had done, but it was a lesson that these systems use that circuit for all kinds of decisions like abs, traction control, etc. As in your case, the code was a brake circuit code.
I see it occasionally on Subaru's and read somewhere that the brake system control module monitors the current flow on the circuit, and will trigger a related DTC. Usually I find one or more bulbs burned out. The #7443 (2 filament) and 7440 (single filament) bulbs will interchange, if one pushes hard enuff :O) In other instances, I've found with the shared dual filament brake and tail light bulbs, a broken filament on the tail light circuit touching the brake light filament. Subaru has a few BLS bulletins, campaigns/recalls, and switch adjustment procedure updates as well.
Had a customer come in with an 18 Toyota Tundra and it wouldn’t allow the gear selector to move. Turns out he installed a new tail light assembly but it did not come with bulbs. Putting a bulb in and replacing the blown fuse for stop lights fixed it. Fuse would blow every time brake pedal was applied without a bulb in it.
Corrosion on my third brake light socket on my 2008 Toyota Corolla disabled my head lamps and high beams. Once I cleaned the green corrosion and a little DeOx they all came back to life. Good job Sir!
I've heard the same problem exists in some late 80's or early 90's cars. The backup bulbs are the "pull" resistors for the circuit. Without the bulbs, the ECM thinks the engine is in gear all the time. When the engine is actually put in gear, the engine stalls as the ECM fails to compensate for the engine load.
I had to watch the video twice to pick up on what you were saying. At first I thought you were saying the relay grounded the circuit down to turn on the light. I had to watch a second time to realize that you were saying the "pull resistors" in the modules are pull up, not pull down. The relay still pulls up to activate the circuit, but that leaves only the bulbs to pull it down to the inactive state.
Wow, wow! Amazing! I loved the video. Three days ago, in 2011 Mitsubishi Lancer a customer complained about losing power doring costing and experiencing a lack of acceleration when they tried to turn on the lights. Upon investigation, I discovered that one of the brake lights was burnt out. I wasn't sure why this happened until I watched your video. Thank you once again!"
I love your videos man. Always learn something, I knew what was up with this one straight away but didn't know the diagram was wrong on it. I always watch your videos and thought I was subscribed and wasn't I am now. Thanks for all the time you put into these to help us all figure these systems out, they are getting more complex everyday.
Very interesting, this indicates that if one or more bulbs were tied in on this third brake light circuit the DTC's must be very distracting😋 Thanks for sharing Bro😍
Wow. Gotta love them OE diagrams. I’ve seen that happening on a Silverado, luckily i threw a high mount bulb in it as well so i just assumed the brake light switch fixed it hahaha now i know what that code actually pertains to. It always stumped me because soon as i see a brake switch code, i immediately check the brake light operation and they work, crazy how 1 bulb being out can cause a circuit issue. Your badass brother
Really enjoy your content and your very well put together videos. Cool hearing your back story with Sean this week. Quite the clever circuit, definitely more than a simple pull up or down resistor going on here so recognizing bias voltage vs voltage drop from unwanted resistance or an open circuit is critical. I still like to trace out my diagrams with color pencil when you get into series-parrallel circuits espically if chasis is providing the unstable high side of the circuit with this particular one being 12V switched on a safety critical circuit. A methodical approach with testing vs guessing like your demonstrate very well is so refreshing and educational to watch. You sure make a guy wanna buy a Pico! Thanks again.
I remember back in the days of Rear Wheel Anti Lock brake systems having a code 9 I think that was it. When you ran the ABS test code 9 came up. When the 3rd stop light bulb went out, there was the code. Great diag and fix!
as soon as you said brake light switch code i thought need to see all brake light bulbs working because cars are getting too smart in a dull way thank you for the videos
The ECM is looking for a pull up signal. The PID changes state when pulled up. The voltage(s) from the ECM and TCM are bias voltages to monitor circuit integrity. Not brake apply detect.
I find that the service manual info only gets you so far. You really have to think about it and read between the lines. If I followed it to the letter, I'd be putting PCMs in Toyotas all the time. Sometimes, the simple stuff can throw you for a bit. Interesting video.
Wow, I've never run into that code yet, but now I'm prepared! Thanks for the Tip! Are you sure it's a pull-down circuit? Can't it be a pull-up and that is just bias voltage to check for circuit integrity?
On my 2004 silverado, I lost my cruise control... Turned out being because I installed an LED bulb in the CHMSL... Put incandescent bulb back in, and cruise control fixed... Thanks for your work...
you would think the bulbs being out in the third brake light would throw a bulb out message as the circuit is monitored for opens. I enjoyed the pod cast Jake👍👍Cheers
Thanks for this video. My daughter owns a 2010 Cobalt and she probably was close to having this code because a while back, two out of the three bulbs in her third brake light were blown.
Nice video and great tip. I remember Eric O. from South Main Auto Repair had mentioned that before about checking the brake lights. Thanks for sharing.
Its looks similar circuit fault when ground is missing on tail lamps it effects other marker and indicator lights.ecm is getting signal pull down through a bulb 💡 😂crazy is that..great great explanation 👍🏿 sir.
I had a similar experience with a Corolla: some sort of brake switch code and the issue was the right side brake bulb had a poor connection to the socket.
I believe the diagram is right in that it is a pull up circuit, the difference is that with the circuit open(bulb blown) you are seeing a bias voltage. The PCM sends out a bias voltage with very little current to check circuit integrity. When the circuit is complete that bias is pulled low. Also if you read in the trouble shooting data right above the circuit system/ testing steps, it states in circuit system/ verification "Inspect for proper operation of the stop lamps, including the CHMSL. Refer to Exterior Lighting Systems Description and Operation" Maybe they should of highlighted that or included it in the circuit system/ testing steps.
Oh I neverrrrrrr would have figured that out and it’s still quite confusing to be honest. I have a Silverado here now with this same issue. Let me find a pedal depressor! 😖🤦🏽♂️
Such a cool thing, right? And you wouldn't believe how many times someone has told me they "have a short to power" on a normally low [if complete] sensed circuit... but, simply because they were testing *only* with a 30 Mohm impedance DVOM... on an *open/unloaded* circuit. And I don't normally use the same setup as you -- with the bulb -- but I always have my fine-tip 40 ohm [Snapon or OTC] testlight with me, and clamped to a good ground... and if I clip the red DVOM lead to the tip of the test light and re-probe the circuit right in front of them, shoosh, the code is gone and the stray circuit voltage drops to zero (as it should). You can actually see the gears start to turn in their head (and that's a good thing). 👍
So that means the ecm ,tcm and bcm need to see 0 volts through the light bulb filament to ground in order to see as "Released", otherwise it'll show 7.5 volts and therefore the P0573. Thanks for sharing.
You can see the challenge in making an ECM and TCM high side switched third tail light full diagnostic circuit (circuit open, circuit shorted to +12VDC, etc.) when you have a center stop lamp to ground and you tie both the ECM and TCM inputs directly to the bulb. You have to assume that the bulb will always pull the circuit towards ground in order to design an analog diagnostic voltage divider (probably pulled to +12VDC through a diode) processed by an A/D channel. I do think that the ECM or the TCM input divider approach is correct, but not when you connect them together. However, we have to ask the question why doesn't the BCM monitor the CHMSL light? To close the loop on diagnostics the controlling module should monitor if the commanded load is turning on, especially if isolated by a relay. There is more strangeness to the circuit. First of all the relay should have a noise suppression device on the relay coil (either a resistor or a diode), and you would put the relay output fuse before the relay switch and not after it. You need to protect the wiring from B+ to the relay in case of a short to ground.
Amazing circuitry imagination my friend, but I think that this design, or circuitry of the Brake Sw., needs to be redesigned. Perhaps with a diode a possible ground return could be solved, or perhaps a +B but this is only my assumption since the circuitry must be extensively analyzed until the problem is solved. VERY GOOD VIDEO. Greetings from Tijuana 🇲🇽 Mexico 👍👍👍
I watch one of your videos and you put some kind of listening device by the back tire and we heard the noise the rear end was making can you tell me what that device was . Like to get one so i can use it to hear where the noise came from. Kept up the good videos. You are going to be one of the best mech on you tube thank you
The ecm and tcm are putting a bias voltage on the circuit that the bulb pulls down, when the bulb blows bias voltage goes up. Just think about it and you will realize the diagram is not wrong.
What is the purpose of the bias voltage on a digital input? Digital inputs are usually high or low and pulled in the opposite direction, no bias. The diagram shows both the TCM and ECM with pull down resistors. So if in fact it was trying to bias for some reason (bad way to check for blown bulbs using two different modules?) the schematic would show the TCM with a pull up. Seems more there is no resistor at all on the TCM or it does have a pull up and it's wrong. But what was your idea with the bias voltage?
I watched your video and none of the conditions applied to the code and I had an intermittent brake light and warning for brake system malfunction and service brake system well my shop foreman came in this morning when I'm off and asked where I left off told him I had battery voltage on the signal wire and good power and ground and the scanner was showing circuit and pedal picking up applied and not applied he said I put brake fluid in it and it's off your fired...
What confuses me: The ECM and TCM are both tied directly to that center light... So if they are applying a high voltage at all times for a pull down circuit-- then why isn't the light ON at all times? How is that ECM pull down circuit using the bulb as a ground without lighting it?
What about whith my is has tha same code i already change the brake switch y still has de code but stop lights when the cars is on the light is on all the time and my car has check engine reduce
You probably have the dual TPS type brake pedal position sensor. One sensor is wired to the BCM and the other sensor is wired to the ECM. The ECM will reduce engine power if it detects the brake pedal and accelerator is applied at the same time. You most likely have a C0277 code. I would perform the relearn procedure on the ECM first followed by the BCM and finally the yaw sensor. Before you do any of that, though I would check all of your bulbs and make sure they are good.
It doesn't make sense to use a pull up on a circuit where you are looking for a high signal. Unless you are monitoring for blown bulbs, but you wouldn't rely on one module to pull high and one to pull low. Plus with the 9V with only the TCM on the circuit it seems more like it's floating and there is no resistor at all. Yeah, the bulbs pull it down and resolve the code, but seems there is still the issue of why is one pulling down and one floating or possibly be pulling up? Nice catch though!
@@autodiagyt Yeah, not wanting to disagree but I deal with control circuits all the time, not necessarily cars anymore. But I think trying to divide the input to hold a middle voltage with two separate modules is a bad design. Have you seen that exact design in anything else besides this and the other cars that use this set up? And I may understand if it was monitoring for bad bulbs AND told you the bulbs were out. But in this case it just seems to be monitoring for brake application when circuit goes high. Therefore it's should be pulled down by both devices looking for the high. But maybe this a GM thing, to use one pull down in one module and one pull up or floating in another, but just doesn't seem best practice at all if that's the case. Especially since it doesn't mention the bulbs in the troubleshooting chart. In any case, still a good find and super easy fix, but it shouldn't have been a problem to begin with, if engineered properly.
@@autodiagyt I see what your saying, but in digital circuits, not analog, there is the threshold voltage. Hence the reason for the pull down or pull up, so you don't get the in between voltages, since a digital input can only detect high or low. It doesn't measure voltage like an analog circuit. I know you know all of this, I just think this is being overthought when it's just a case of poor engineering on GMs part, especially given the troubleshooting makes no mention of bulbs. Or, the TCM pull down is bad or never designed in. But pretty sure you mentioned this exact symptom and cause in other GM vehicles. Curious as to the troubleshooting chart for the always low code and how that chart would play with your thinking with the multiple voltages. Anyway, thanks for having the discussion, maybe there is something we are both missing?
I have that code. Put a new brake switch and all my taillights stay on even without the harness connected to the brake switch. Im check the bulb tomorrow.
Talk about misleading information! Throw a code for a brake pedal switch when a bulb is bad! And with the schematic wrong, it's no wonder people go down that rabbit hole. Great case, Jake!
good god thk for this video, wow very impressed with you working it out, so it need the resistance of good light bulbs in circuit, gm lead tech down rabbit hole isn't that nice.
That was cool, Jake! Now if this was a European car, it would tell you on the message center exactly which bulb was burnt out... Because Euro cars are superior to all other cars 😆
I was a young mechanic working in NW Pennsylvania in 1986 when the "third brake light" was first required on all vehicles and being certified to do inspections I knew it as a collision avoidance light. Thank you for another video with invaluable information. You are the best!
Great diagnosis
That's a downright eye opener thank you.
I always wondered if the manufactures go back and revise their wiring diagrams after finding out how many good techs have been misled by this kind of stuff. Thanks so much for educating us Jake!
I had a similar experience with a Subaru, which locked itself in park when the rear right brake light fuse was blown. I had put an incorrect replacement bulb in for a blown bulb, and it blew the circuit fuse, and that prompted the car to lock itself in park for safety. The diagnosis was easy because I knew what I had done, but it was a lesson that these systems use that circuit for all kinds of decisions like abs, traction control, etc. As in your case, the code was a brake circuit code.
I see it occasionally on Subaru's and read somewhere that the brake system control module monitors the current flow on the circuit, and will trigger a related DTC.
Usually I find one or more bulbs burned out.
The #7443 (2 filament) and 7440 (single filament) bulbs will interchange, if one pushes hard enuff :O)
In other instances, I've found with the shared dual filament brake and tail light bulbs, a broken filament on the tail light circuit touching the brake light filament.
Subaru has a few BLS bulletins, campaigns/recalls, and switch adjustment procedure updates as well.
Had a customer come in with an 18 Toyota Tundra and it wouldn’t allow the gear selector to move. Turns out he installed a new tail light assembly but it did not come with bulbs. Putting a bulb in and replacing the blown fuse for stop lights fixed it. Fuse would blow every time brake pedal was applied without a bulb in it.
As Ivan would say this is so cool!
i had one of those about a year ago never figured it out customer didn't want to pay for a full diag thanks so much very helpful information
Corrosion on my third brake light socket on my 2008 Toyota Corolla disabled my head lamps and high beams. Once I cleaned the green corrosion and a little DeOx they all came back to life.
Good job Sir!
Id like some info on the test leads you have and some of the other equipment you use. Great Channel!
I've heard the same problem exists in some late 80's or early 90's cars. The backup bulbs are the "pull" resistors for the circuit. Without the bulbs, the ECM thinks the engine is in gear all the time. When the engine is actually put in gear, the engine stalls as the ECM fails to compensate for the engine load.
17:49 Jake you write letter to Alldata and they add to TSB?
I guess I've just gotten lucky. But I'll be making sure I check that from now on. You're awesome
I appreciate the screen share that eliminates glare and pointers edited in for visuals.
Thanks I try doing the best videos I can. I don't always have time to do it but I try
I had to watch the video twice to pick up on what you were saying. At first I thought you were saying the relay grounded the circuit down to turn on the light. I had to watch a second time to realize that you were saying the "pull resistors" in the modules are pull up, not pull down. The relay still pulls up to activate the circuit, but that leaves only the bulbs to pull it down to the inactive state.
Wow, wow! Amazing! I loved the video. Three days ago, in 2011 Mitsubishi Lancer a customer complained about losing power doring costing and experiencing a lack of acceleration when they tried to turn on the lights. Upon investigation, I discovered that one of the brake lights was burnt out. I wasn't sure why this happened until I watched your video. Thank you once again!"
I love your videos man. Always learn something, I knew what was up with this one straight away but didn't know the diagram was wrong on it. I always watch your videos and thought I was subscribed and wasn't I am now. Thanks for all the time you put into these to help us all figure these systems out, they are getting more complex everyday.
I hope one of you contacted Alldata and told them the diagram was wrong. Thanks for the videos. Been doing his for 40 years. Always learning.
It's not alldata diagram. That is straight from the manufacturer.
Very interesting, this indicates that if one or more bulbs were tied in on this third brake light circuit the DTC's must be very distracting😋
Thanks for sharing Bro😍
Is it just resistance in the circuit of the hight bulbs
AS SOON AS YOU WENT TO THE DIAGRAM MY HUNCH WAS A BRAKE BULB ISSUE.NICE JOB!!
Wow. Gotta love them OE diagrams. I’ve seen that happening on a Silverado, luckily i threw a high mount bulb in it as well so i just assumed the brake light switch fixed it hahaha now i know what that code actually pertains to. It always stumped me because soon as i see a brake switch code, i immediately check the brake light operation and they work, crazy how 1 bulb being out can cause a circuit issue. Your badass brother
Wow that is crazy , a brake code for burnt bulbs . Another informative video thank you👍🏼👍🏼👍🏼👍🏼👍🏼
Really enjoy your content and your very well put together videos. Cool hearing your back story with Sean this week. Quite the clever circuit, definitely more than a simple pull up or down resistor going on here so recognizing bias voltage vs voltage drop from unwanted resistance or an open circuit is critical. I still like to trace out my diagrams with color pencil when you get into series-parrallel circuits espically if chasis is providing the unstable high side of the circuit with this particular one being 12V switched on a safety critical circuit. A methodical approach with testing vs guessing like your demonstrate very well is so refreshing and educational to watch. You sure make a guy wanna buy a Pico! Thanks again.
I remember back in the days of Rear Wheel Anti Lock brake systems having a code 9 I think that was it. When you ran the ABS test code 9 came up. When the 3rd stop light bulb went out, there was the code.
Great diag and fix!
as soon as you said brake light switch code i thought need to see all brake light bulbs working because cars are getting too smart in a dull way thank you for the videos
The ECM is looking for a pull up signal. The PID changes state when pulled up. The voltage(s) from the ECM and TCM are bias voltages to monitor circuit integrity. Not brake apply detect.
I find that the service manual info only gets you so far. You really have to think about it and read between the lines. If I followed it to the letter, I'd be putting PCMs in Toyotas all the time. Sometimes, the simple stuff can throw you for a bit. Interesting video.
Very true!
That's some amazing work you do. Thank you for helping out everyone else for posting these findings. 👍😁
Wow, I've never run into that code yet, but now I'm prepared! Thanks for the Tip! Are you sure it's a pull-down circuit? Can't it be a pull-up and that is just bias voltage to check for circuit integrity?
Really cool.. I have to look at a diagram to see why u only have 7v with bad bulbs.. nice video
@@autodiagyt I watched it again, now I understand.. that’s really interesting, never saw that before ty for showing us!
Wow what a find thanks muncho for sharing Jake
On my 2004 silverado, I lost my cruise control... Turned out being because I installed an LED bulb in the CHMSL... Put incandescent bulb back in, and cruise control fixed... Thanks for your work...
Snapon tip doesn’t work. I tried lol.
JAKE, AWESOME approach and diagnoses thanks for sharing.
you would think the bulbs being out in the third brake light would throw a bulb out message as the circuit is monitored for opens. I enjoyed the pod cast Jake👍👍Cheers
Very informative video!!
Thanks again for valuable info!!!!!
Great video very helpful solved my problem before I spent alot of time on it THANKS!
Incredible info. Thanks Jake.
Thanks for this video. My daughter owns a 2010 Cobalt and she probably was close to having this code because a while back, two out of the three bulbs in her third brake light were blown.
You learn something new everyday! 😁
I expected it very early on :-) VW has the same "issue" with many Cars.....blown bulb and Brake Switch Errorcode. And Cruise Control does not work :-)
Awesome job Jake! I kinda laughed at the end with you. Great diag and hugely informative for anyone who may experience this in the future. Thanks bud!
Nice video and great tip. I remember Eric O. from South Main Auto Repair had mentioned that before about checking the brake lights. Thanks for sharing.
I would really like to know how u made your test light tied into your dvom .Great job though 👍
Love your videos.. excellent knowledge
Its looks similar circuit fault when ground is missing on tail lamps it effects other marker and indicator lights.ecm is getting signal pull down through a bulb 💡 😂crazy is that..great great explanation 👍🏿 sir.
Very interesting so TCM or ECM actually loking ground through third brake bulb
@@autodiagyt Thank you for provide us with very usefull information
I had a similar experience with a Corolla: some sort of brake switch code and the issue was the right side brake bulb had a poor connection to the socket.
Nice job for fixing the problem..
I believe the diagram is right in that it is a pull up circuit, the difference is that with the circuit open(bulb blown) you are seeing a bias voltage. The PCM sends out a bias voltage with very little current to check circuit integrity. When the circuit is complete that bias is pulled low.
Also if you read in the trouble shooting data right above the circuit system/ testing steps, it states in circuit system/ verification "Inspect for proper operation of the stop lamps, including the CHMSL. Refer to Exterior Lighting Systems Description and Operation" Maybe they should of highlighted that or included it in the circuit system/ testing steps.
Keep these videos coming!!
Lmao 🤣 I love this excellent video. Tbh the voltage would throw me off but id would of check the bulb function 😂.
Jake, those brake lights always seem to mess me up, not to mention what happens when the diagram is wrong. Thanks for Sharing! 🙃🙂🙂
that's nuts. seems that should not be the way? Thanks charlie ,wis.
Thank you!
Priceless
Well done 👍
Alright Jake, pretty interesting!!!
Good morning and keep up the great work!! Great video!
Oh I neverrrrrrr would have figured that out and it’s still quite confusing to be honest. I have a Silverado here now with this same issue. Let me find a pedal depressor! 😖🤦🏽♂️
You're not getting my 4 by 2, go to the lumber yard and fetch your own. D'ya think they grow on trees??
Wow that blew my mind 😮
Such a cool thing, right? And you wouldn't believe how many times someone has told me they "have a short to power" on a normally low [if complete] sensed circuit... but, simply because they were testing *only* with a 30 Mohm impedance DVOM... on an *open/unloaded* circuit.
And I don't normally use the same setup as you -- with the bulb -- but I always have my fine-tip 40 ohm [Snapon or OTC] testlight with me, and clamped to a good ground...
and if I clip the red DVOM lead to the tip of the test light and re-probe the circuit right in front of them, shoosh, the code is gone and the stray circuit voltage drops to zero (as it should).
You can actually see the gears start to turn in their head (and that's a good thing). 👍
So that means the ecm ,tcm and bcm need to see 0 volts through the light bulb filament to ground in order to see as "Released", otherwise it'll show 7.5 volts and therefore the P0573. Thanks for sharing.
Thank you sir for sharing your knowledge
❤ thanks for sharing nice work
You can see the challenge in making an ECM and TCM high side switched third tail light full diagnostic circuit (circuit open, circuit shorted to +12VDC, etc.) when you have a center stop lamp to ground and you tie both the ECM and TCM inputs directly to the bulb. You have to assume that the bulb will always pull the circuit towards ground in order to design an analog diagnostic voltage divider (probably pulled to +12VDC through a diode) processed by an A/D channel. I do think that the ECM or the TCM input divider approach is correct, but not when you connect them together. However, we have to ask the question why doesn't the BCM monitor the CHMSL light? To close the loop on diagnostics the controlling module should monitor if the commanded load is turning on, especially if isolated by a relay.
There is more strangeness to the circuit. First of all the relay should have a noise suppression device on the relay coil (either a resistor or a diode), and you would put the relay output fuse before the relay switch and not after it. You need to protect the wiring from B+ to the relay in case of a short to ground.
Wow …… thank you really good video
Great information
another reason to check all lights before diag.
Top diagnose!
SHARP Automotive Diagnostics & Programming
👍
From Nick Ayivor from London England UK 🇬🇧 ⏰️ 21:33pm
SHREWD
SHARP
QUICK-WITTED Automotive Diagnostics & Programming
❤️ it
From Nick Ayivor from London England UK 🇬🇧 ⏰️ 07:40am Good Morning 🙏 🌄
Amazing circuitry imagination my friend, but I think that this design, or circuitry of the Brake Sw., needs to be redesigned. Perhaps with a diode a possible ground return could be solved, or perhaps a +B but this is only my assumption since the circuitry must be extensively analyzed until the problem is solved. VERY GOOD VIDEO. Greetings from Tijuana 🇲🇽 Mexico 👍👍👍
Had a Toyota Avensis in Europe with this kind of problem. It was lightin up abs light. Weird design 😅
Great find..!
I watch one of your videos and you put some kind of listening device by the back tire and we heard the noise the rear end was making can you tell me what that device was . Like to get one so i can use it to hear where the noise came from. Kept up the good videos. You are going to be one of the best mech on you tube thank you
It’s just my microphone I record videos with lol
@@autodiagyt thank you for your reply
Way cool tip 👊🏻. Keep these coming
thanks excellent
Thank you very much ❤❤❤
The ecm and tcm are putting a bias voltage on the circuit that the bulb pulls down, when the bulb blows bias voltage goes up. Just think about it and you will realize the diagram is not wrong.
What is the purpose of the bias voltage on a digital input? Digital inputs are usually high or low and pulled in the opposite direction, no bias. The diagram shows both the TCM and ECM with pull down resistors. So if in fact it was trying to bias for some reason (bad way to check for blown bulbs using two different modules?) the schematic would show the TCM with a pull up. Seems more there is no resistor at all on the TCM or it does have a pull up and it's wrong. But what was your idea with the bias voltage?
Sorry, you are right, the diagram is wrong
Thank you sir...
smart man for sour 👍👍👍👍👍
ty great info. Outro should be your intro tho,.
I watched your video and none of the conditions applied to the code and I had an intermittent brake light and warning for brake system malfunction and service brake system well my shop foreman came in this morning when I'm off and asked where I left off told him I had battery voltage on the signal wire and good power and ground and the scanner was showing circuit and pedal picking up applied and not applied he said I put brake fluid in it and it's off your fired...
That’s terrible
What confuses me: The ECM and TCM are both tied directly to that center light...
So if they are applying a high voltage at all times for a pull down circuit-- then why isn't the light ON at all times? How is that ECM pull down circuit using the bulb as a ground without lighting it?
What about whith my is has tha same code i already change the brake switch y still has de code but stop lights when the cars is on the light is on all the time and my car has check engine reduce
Sounds like you have a different issue if you have reduced engine power message
@@autodiagyt in dash no say nothing but is like power engine reduce
You probably have the dual TPS type brake pedal position sensor. One sensor is wired to the BCM and the other sensor is wired to the ECM. The ECM will reduce engine power if it detects the brake pedal and accelerator is applied at the same time. You most likely have a C0277 code. I would perform the relearn procedure on the ECM first followed by the BCM and finally the yaw sensor. Before you do any of that, though I would check all of your bulbs and make sure they are good.
Learning to read schematics, will help you diagnose what others cant.
Thats what separates a mechanic from a technician.......
that was a good one
Awesome 😅
It doesn't make sense to use a pull up on a circuit where you are looking for a high signal. Unless you are monitoring for blown bulbs, but you wouldn't rely on one module to pull high and one to pull low. Plus with the 9V with only the TCM on the circuit it seems more like it's floating and there is no resistor at all. Yeah, the bulbs pull it down and resolve the code, but seems there is still the issue of why is one pulling down and one floating or possibly be pulling up? Nice catch though!
@@autodiagyt Yeah, not wanting to disagree but I deal with control circuits all the time, not necessarily cars anymore. But I think trying to divide the input to hold a middle voltage with two separate modules is a bad design. Have you seen that exact design in anything else besides this and the other cars that use this set up? And I may understand if it was monitoring for bad bulbs AND told you the bulbs were out. But in this case it just seems to be monitoring for brake application when circuit goes high. Therefore it's should be pulled down by both devices looking for the high. But maybe this a GM thing, to use one pull down in one module and one pull up or floating in another, but just doesn't seem best practice at all if that's the case. Especially since it doesn't mention the bulbs in the troubleshooting chart. In any case, still a good find and super easy fix, but it shouldn't have been a problem to begin with, if engineered properly.
@@autodiagyt I see what your saying, but in digital circuits, not analog, there is the threshold voltage. Hence the reason for the pull down or pull up, so you don't get the in between voltages, since a digital input can only detect high or low. It doesn't measure voltage like an analog circuit. I know you know all of this, I just think this is being overthought when it's just a case of poor engineering on GMs part, especially given the troubleshooting makes no mention of bulbs. Or, the TCM pull down is bad or never designed in. But pretty sure you mentioned this exact symptom and cause in other GM vehicles. Curious as to the troubleshooting chart for the always low code and how that chart would play with your thinking with the multiple voltages. Anyway, thanks for having the discussion, maybe there is something we are both missing?
I have that code. Put a new brake switch and all my taillights stay on even without the harness connected to the brake switch. Im check the bulb tomorrow.
Some days of these brake switches also need to be relearned with a scantool.
Grasias
I need your help
Can you tell me what is the code exactly
U0010-88
On jeep renegade
@@autodiagyt
Jeep renegade 2019
Code: U0010-88
Very useful and enjoyable tip of info
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This is a lot like Nissan with their transmission code that sets when a brake light is out.
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Talk about misleading information! Throw a code for a brake pedal switch when a bulb is bad! And with the schematic wrong, it's no wonder people go down that rabbit hole. Great case, Jake!
nice one Jake ,crack open a beer for yourself good job
That blows my mind see what I did there 👍
good god thk for this video, wow very impressed with you working it out, so it need the resistance of good light bulbs in circuit, gm lead tech down rabbit hole isn't that nice.
Like Hyundai kia trans in limp from water in back up lamps 😅
🤣🤣🤣 that was awesome