I read that too, but that is for the older model excavators. On those machines the AI motor is under the seat. As you can see in one of my videos there is no module under the seat. The pin that connects to the throttle knob assembly has 8 pins; something tells me the AI motor was consolidated into the main control board and the throttle knob. I also have yet to find a manual that instructs on how to set up the AI to add insult to injury I may be close to solving this once and for all after much trial and error. If successful I'll post a video. It's been quite the frustrating experience
I ended up replacing the entire wiring harness as well. Probably could have saved a lot of money if I took the time to test all wires with a multimeter. Did replacing the harness fix your problem as well?
There is a pressure switch in the circuit, so when you move a control the machine sensors the pressure and auto raises the engine speed, I can explain how to test it if you’re still having issues?
Thank you for the offer to help Dan! I'd definitely like to know how to test this pressure switch if you can do so in the comments section. What ultimately happened here was the entire machine wiring harness was replaced. There was a short somewhere in the wiring, which was preventing the proper signal from getting to the control board. With no readable parameters the machine was unable to calibrate itself and move the throttle properly. The damage in the wiring harness also shorted out the new throttle knob assembly panel, so in this case the issue was not just a bad pressure switch. However please do share whatever details you can to help others who may be in a similar spot and don't want to pay large sums to a dealership
@@PrimitivePeter based on the wiring diagram I have the pressure switch is powered by the meter fuse and then into the control panel. There are two plugs on the back of the control panel, plug 1 has 22 pins, and looking from the back of the plug number 1 pin is the top left (top of the plug has the lock tab). PIN number 8 will be from the pressure switch. Withe ignition on there should be power to that pin, you’ll need something pretty small to push in beside the wire into the back of the plug. If there’s no power there chances are the pressure switch has failed but also the wires to it tend to get hot and brittle and can break easily Also plug 2 (the 20 pin plug) pin 4 is the wire from the throttle dial, if you back probe that one you should see the voltage increase and decrease as you turn the throttle dial. Hope that helps
Oh another question, where did you find the info letting you know how to enter into the “Service Mode?” That’s a VALUABLE source wherever you found it!! Cheers
I did a lot of searching for the shop manual for this machine and found it online somewhere. Can't remember if it was on a forum or posted on a website like manualslib.com. Hope your issue with the governor sensor is way more simple. I spent 4k having the entire engine wiring harness replaced, so do your best to find the bad connection on your machine and save a boatload of cash!
Sounds like the accelerator motor same issue I have with my Kubota I changed everything and it turned out to be the accelerator motor under the floorboard
Replacing the entire engine harness at a cost of nearly 4k ultimately solved the issue. What I believe was happening is there was a short to ground somewhere in the wiring which was preventing the correct signal to reach the control board, so the computer did not know where to adjust throttle in relation to engine speed. The comment below from @DanMadeau mentions how to test the throttle knob to see if it's working properly by changing voltage as the knob is turned. I would test the throttle knob before buying a new one. I would not recommend firing the parts cannon at it like I did. Replacing the engine speed sensor would be the easiest and cheapest place to start. With your 121 the engine is facing 180 degrees opposite mine and all sensors are much easier to get to so you have a lucky break there. If you don't want to replace the entire harness, start chasing wires and check all the relays under the seat. Mice love to make nests in these things and can cause havoc. Get a multimeter that can test continuity and DC voltage. Good luck and let me know what turns up
I need to look at the old wiring harness and see if there's an obvious short/ burned wire. The entire machine wiring harness was replaced at a cost of nearly 4k. In hindsight you could probably chase down the problem using a multimeter, provided you have a shop manual that gives the voltage/ amperage readings of what each sensor is supposed to put out. The auto idle system takes readings from the governor sensor located on the top of the injection pump by the throttle linkage and the engine speed sensor which reads a tone ring on the crankshaft. With your 121 these sensors will be facing you when you open the hood, unlike on my machine where you have to go under the seat through a cover to access the ESS. With these two readings the computer tells the auto idle motor located under the platform near the battery where and how far to move the throttle cable. I just replaced the sensors to no avail. Along with the auto idle motor and the throttle assembly knob on the instrument cluster next to the meter. If you have the time and motivation chase every single wire from sensor to control board and see if you can find anything. What is happening is the computer is not getting an accurate reading from somewhere in the system to determine throttle position and/ or engine speed and throwing the code. There's a series of connections under the seat; I don't know if those are just plugs or relays. But those could be part of the problem too if any of the aforementioned sensors goes to the plug/ relay. Bad grounds could also cause an open circuit which would give an improper reading, but I don't know if/ where the grounds are for the machine outside of the battery. This is essentially a bad wiring issue causing a big headache. I would chase all wires first. If you want to start with the easiest and cheapest sensors replace the engine speed sensor and governor sensors. You may get lucky. At the very least remove the control board and throttle knob assembly panel to see if there's a shorted connection under there. Or chase wires starting from the throttle knob. I'll try to dig up the old harness and see if anything is obvious. Good luck and keep me posted, hope you can do it for cheaper than me. How do you like the 121? I sometimes want to upgrade to the 121, but only an older Tier 3 model like my 91
I have a similar problem on my KX 161-3. It suddenly one day showed an error message of “Governor Sensor.” Did yours also show that error as well? I haven’t torn the thing apart yet as I dread the coming frustration I know will ensue. I don’t happen to have a huge amount of patience and this job , now my own house has turned into the nightmares you only read about and it’s about to turn me into a “For Sale” guy if it continues much more….
You may be lucky, the governor sensor is more simple to replace and not as involved as the dreaded "accel sensor". With your machine being a 161 the engine is flipped the other way compared to mine so the side of the engine with the governor sensor will be facing you when you open the hood. The governor sensor is essentially the throttle position sensor. The sensor is part of the throttle linkage on the injection pump, held in by one bolt. Look up exploded parts diagrams on a site like Messicks and you'll see where it's located in better detail. Does your machine still run fine or will it not accelerate or decelerate like mine was doing? This is a simple electronic issue, don't lose hope in the machine yet. If replacing the sensor doesn't solve the problem find a manual that gives resistance values for the sensors and use a multimeter to see if you're getting proper voltage readings at the sensors in question. A bad ground or shorted wire will cause all sorts of issues like this but in reality patching or replacing a chewed/ worn through wire is a simple fix. Good luck and keep us posted
@@PrimitivePeter. Peter, THANKS SO MUCH for the suggestions. I am about to tear into today, crossing my fingers on this and sure will follow your advice on the manual library site you suggested on the prior message and everything here. Will let you know what I find. Oh, forgot to answer you question. My machine will run, but only at idle. The throttle dial in the cab is non responsive, so the machine just sits there and idles at the factory default idle RPM. I have a long history on this property with Pack Rats making nests in vehicles and in this machine as well. Really hoping that they haven’t gotten in there and stripped out a bunch of deeply buried wires. Some of my neighbors and I have spent many thousands on wiring harnesses and other type parts because of these damn rats.
@@freeandcriticalthinker4431 Happy to help. Here's a link to the manual I used:kattrak.com/wp-content/uploads/Service-Manual-Kubota-KX91-3-KX101-3-KX121-3-KX161-3-U35-3-U45-3.pdf If the throttle knob isn't working then there's definitely an electrical issue. Mine did the same thing. And if you have a known problem with rodents on your property you likely have a chewed wire somewhere. A lot of the wires run under the seat and connect to relays there. Make sure everything under the seat is plugged in and secure. I put a tray of poison under the seat every fall/ winter to kill anything that wants to nest in the machine. A new governor sensor should be under $100 so not too unreasonable to replace and see if you get lucky. Otherwise look through the manual (it's long, I know) and see if you can find voltage readings for each sensor. Find where the sensor connects to the control board and use a multimeter to test voltage. The governor sensor has a little tab on it that moves with the throttle cable. You can remove the sensor but leave it plugged in and manually move the sensor to see if the voltage changes. If nothing changes it's either the sensor or a break in the wire. Keep chasing wires and take deep breaths. Time spent troubleshooting yourself is money saved at the dealership!
@@PrimitivePeter Peter, I got super LUCKY! I traced back the governor motor which appears to be on the back of the engine and well “Son of a Bitch” I found all three wires connecting it had been cut somehow. Six barrel connectors and 45 mins later and I was in business! No dismantling anything other than having to cut a couple cable anchors away so I could work and that was it. What a relief as your story and another fellows videos painted a dismal picture of what was in store for me. Regardless though THANKS SO MUCH for your suggestions, links and help. Really do appreciate that. Cheers Chad
@@freeandcriticalthinker4431 Awesome! Glad it was simple for you. When you say governor motor was it the governor sensor or something else? Not sure if you can post pictures here but if you have a link to the part with the cut wires it could help someone else reading this down the road. Awesome you didn't waste lots of time and money like I did, happy digging!
Yes it was a wiring issue. I ended up having the whole engine harness replaced at a cost of nearly 4k. If you look at my replies to the other comments on here you'll see some discussion of the problem and solutions. If you have a multimeter and know the resistance or voltage values for each sensor you can diagnose and chase down exactly where the short to ground is coming from
Did you find out what the issue was? I ended up having to replace the entire wiring harness. Which means it was probably a bad ground somewhere as the sensor wasn't reading correctly to communicate with the computer. Please share what you came up with as two heads are better than one!
Oh and Thx! I couldn’t find that sep up procedure in the workshop manual and it worked a treat! Cheers
I read somewhere in the workshop manual that you have to unplug the 8 pin plug from the ai motor then program it and then plug it back in
I read that too, but that is for the older model excavators. On those machines the AI motor is under the seat. As you can see in one of my videos there is no module under the seat. The pin that connects to the throttle knob assembly has 8 pins; something tells me the AI motor was consolidated into the main control board and the throttle knob.
I also have yet to find a manual that instructs on how to set up the AI to add insult to injury
I may be close to solving this once and for all after much trial and error. If successful I'll post a video. It's been quite the frustrating experience
Sir, did you find the problem? I have a u35-4 kubota with the same problem but I already replaced all the wiring in the machine a year ago
I ended up replacing the entire wiring harness as well. Probably could have saved a lot of money if I took the time to test all wires with a multimeter. Did replacing the harness fix your problem as well?
There is a pressure switch in the circuit, so when you move a control the machine sensors the pressure and auto raises the engine speed, I can explain how to test it if you’re still having issues?
Thank you for the offer to help Dan! I'd definitely like to know how to test this pressure switch if you can do so in the comments section.
What ultimately happened here was the entire machine wiring harness was replaced. There was a short somewhere in the wiring, which was preventing the proper signal from getting to the control board. With no readable parameters the machine was unable to calibrate itself and move the throttle properly. The damage in the wiring harness also shorted out the new throttle knob assembly panel, so in this case the issue was not just a bad pressure switch. However please do share whatever details you can to help others who may be in a similar spot and don't want to pay large sums to a dealership
@@PrimitivePeter based on the wiring diagram I have the pressure switch is powered by the meter fuse and then into the control panel. There are two plugs on the back of the control panel, plug 1 has 22 pins, and looking from the back of the plug number 1 pin is the top left (top of the plug has the lock tab). PIN number 8 will be from the pressure switch. Withe ignition on there should be power to that pin, you’ll need something pretty small to push in beside the wire into the back of the plug.
If there’s no power there chances are the pressure switch has failed but also the wires to it tend to get hot and brittle and can break easily
Also plug 2 (the 20 pin plug) pin 4 is the wire from the throttle dial, if you back probe that one you should see the voltage increase and decrease as you turn the throttle dial.
Hope that helps
Oh another question, where did you find the info letting you know how to enter into the “Service Mode?” That’s a VALUABLE source wherever you found it!! Cheers
I did a lot of searching for the shop manual for this machine and found it online somewhere. Can't remember if it was on a forum or posted on a website like manualslib.com. Hope your issue with the governor sensor is way more simple. I spent 4k having the entire engine wiring harness replaced, so do your best to find the bad connection on your machine and save a boatload of cash!
Sounds like the accelerator motor same issue I have with my Kubota I changed everything and it turned out to be the accelerator motor under the floorboard
Did you ever figure out the accel sensor 11 code, I have a 121 doing the same thing
Replacing the entire engine harness at a cost of nearly 4k ultimately solved the issue. What I believe was happening is there was a short to ground somewhere in the wiring which was preventing the correct signal to reach the control board, so the computer did not know where to adjust throttle in relation to engine speed.
The comment below from @DanMadeau mentions how to test the throttle knob to see if it's working properly by changing voltage as the knob is turned.
I would test the throttle knob before buying a new one. I would not recommend firing the parts cannon at it like I did. Replacing the engine speed sensor would be the easiest and cheapest place to start. With your 121 the engine is facing 180 degrees opposite mine and all sensors are much easier to get to so you have a lucky break there.
If you don't want to replace the entire harness, start chasing wires and check all the relays under the seat. Mice love to make nests in these things and can cause havoc. Get a multimeter that can test continuity and DC voltage. Good luck and let me know what turns up
Have you ever figured out what exactly the problem was?
I’m dealing with the same issue currently on my 121-3
I need to look at the old wiring harness and see if there's an obvious short/ burned wire. The entire machine wiring harness was replaced at a cost of nearly 4k. In hindsight you could probably chase down the problem using a multimeter, provided you have a shop manual that gives the voltage/ amperage readings of what each sensor is supposed to put out.
The auto idle system takes readings from the governor sensor located on the top of the injection pump by the throttle linkage and the engine speed sensor which reads a tone ring on the crankshaft. With your 121 these sensors will be facing you when you open the hood, unlike on my machine where you have to go under the seat through a cover to access the ESS. With these two readings the computer tells the auto idle motor located under the platform near the battery where and how far to move the throttle cable.
I just replaced the sensors to no avail. Along with the auto idle motor and the throttle assembly knob on the instrument cluster next to the meter. If you have the time and motivation chase every single wire from sensor to control board and see if you can find anything. What is happening is the computer is not getting an accurate reading from somewhere in the system to determine throttle position and/ or engine speed and throwing the code. There's a series of connections under the seat; I don't know if those are just plugs or relays. But those could be part of the problem too if any of the aforementioned sensors goes to the plug/ relay. Bad grounds could also cause an open circuit which would give an improper reading, but I don't know if/ where the grounds are for the machine outside of the battery.
This is essentially a bad wiring issue causing a big headache. I would chase all wires first. If you want to start with the easiest and cheapest sensors replace the engine speed sensor and governor sensors. You may get lucky. At the very least remove the control board and throttle knob assembly panel to see if there's a shorted connection under there. Or chase wires starting from the throttle knob.
I'll try to dig up the old harness and see if anything is obvious. Good luck and keep me posted, hope you can do it for cheaper than me. How do you like the 121? I sometimes want to upgrade to the 121, but only an older Tier 3 model like my 91
I have a similar problem on my KX 161-3. It suddenly one day showed an error message of “Governor Sensor.” Did yours also show that error as well? I haven’t torn the thing apart yet as I dread the coming frustration I know will ensue. I don’t happen to have a huge amount of patience and this job , now my own house has turned into the nightmares you only read about and it’s about to turn me into a “For Sale” guy if it continues much more….
You may be lucky, the governor sensor is more simple to replace and not as involved as the dreaded "accel sensor". With your machine being a 161 the engine is flipped the other way compared to mine so the side of the engine with the governor sensor will be facing you when you open the hood. The governor sensor is essentially the throttle position sensor. The sensor is part of the throttle linkage on the injection pump, held in by one bolt. Look up exploded parts diagrams on a site like Messicks and you'll see where it's located in better detail. Does your machine still run fine or will it not accelerate or decelerate like mine was doing?
This is a simple electronic issue, don't lose hope in the machine yet. If replacing the sensor doesn't solve the problem find a manual that gives resistance values for the sensors and use a multimeter to see if you're getting proper voltage readings at the sensors in question. A bad ground or shorted wire will cause all sorts of issues like this but in reality patching or replacing a chewed/ worn through wire is a simple fix. Good luck and keep us posted
@@PrimitivePeter.
Peter, THANKS SO MUCH for the suggestions. I am about to tear into today, crossing my fingers on this and sure will follow your advice on the manual library site you suggested on the prior message and everything here.
Will let you know what I find. Oh, forgot to answer you question. My machine will run, but only at idle. The throttle dial in the cab is non responsive, so the machine just sits there and idles at the factory default idle RPM. I have a long history on this property with Pack Rats making nests in vehicles and in this machine as well. Really hoping that they haven’t gotten in there and stripped out a bunch of deeply buried wires. Some of my neighbors and I have spent many thousands on wiring harnesses and other type parts because of these damn rats.
@@freeandcriticalthinker4431 Happy to help. Here's a link to the manual I used:kattrak.com/wp-content/uploads/Service-Manual-Kubota-KX91-3-KX101-3-KX121-3-KX161-3-U35-3-U45-3.pdf
If the throttle knob isn't working then there's definitely an electrical issue. Mine did the same thing. And if you have a known problem with rodents on your property you likely have a chewed wire somewhere.
A lot of the wires run under the seat and connect to relays there. Make sure everything under the seat is plugged in and secure. I put a tray of poison under the seat every fall/ winter to kill anything that wants to nest in the machine.
A new governor sensor should be under $100 so not too unreasonable to replace and see if you get lucky. Otherwise look through the manual (it's long, I know) and see if you can find voltage readings for each sensor. Find where the sensor connects to the control board and use a multimeter to test voltage. The governor sensor has a little tab on it that moves with the throttle cable. You can remove the sensor but leave it plugged in and manually move the sensor to see if the voltage changes. If nothing changes it's either the sensor or a break in the wire. Keep chasing wires and take deep breaths. Time spent troubleshooting yourself is money saved at the dealership!
@@PrimitivePeter Peter, I got super LUCKY! I traced back the governor motor which appears to be on the back of the engine and well “Son of a Bitch” I found all three wires connecting it had been cut somehow. Six barrel connectors and 45 mins later and I was in business! No dismantling anything other than having to cut a couple cable anchors away so I could work and that was it. What a relief as your story and another fellows videos painted a dismal picture of what was in store for me. Regardless though THANKS SO MUCH for your suggestions, links and help. Really do appreciate that. Cheers Chad
@@freeandcriticalthinker4431 Awesome! Glad it was simple for you. When you say governor motor was it the governor sensor or something else? Not sure if you can post pictures here but if you have a link to the part with the cut wires it could help someone else reading this down the road. Awesome you didn't waste lots of time and money like I did, happy digging!
did you ever get this fixed ?
Yes it was a wiring issue. I ended up having the whole engine harness replaced at a cost of nearly 4k. If you look at my replies to the other comments on here you'll see some discussion of the problem and solutions. If you have a multimeter and know the resistance or voltage values for each sensor you can diagnose and chase down exactly where the short to ground is coming from
I think I can help you with it
I have same issue with my Kobota kx91-3
Did you find out what the issue was? I ended up having to replace the entire wiring harness. Which means it was probably a bad ground somewhere as the sensor wasn't reading correctly to communicate with the computer. Please share what you came up with as two heads are better than one!
@@PrimitivePeter it can be easily fixed if you have a multimeter
@@PrimitivePeter I had the same issue but I repaired the wiring harness
@@arugamadam1956 Where/ what wire was the issue? Where you testing continuity, DC voltage/ amperage, something else with the multimeter?
did you ever get this fixed ?