Allison 5sp: Abs codes c0035/0040 and U1000

[Devon]

These are the codes we found when we scanned my truck to read the abs codes. Both front wheel speed sensors and communication between ECM/TCM(u1000). Truck starts up fine and doesn't die or anything. It's just that the transmission shifts harsh
Under wot. Sometimes between 3-4 and sometimes 4-5 and downshifts harsh sometimes too. Why are these codes being thrown and can these effect Trans? Wheel bearings are fine aswell!? I'm kind of at loss with all this and just want to get to the bottom of this issue. Thanks!


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[S Phinney]

These are the codes we found when we scanned my truck to read the abs codes. Both front wheel speed sensors and communication between ECM/TCM(u1000). Truck starts up fine and doesn't die or anything. It's just that the transmission shifts harsh
Under wot. Sometimes between 3-4 and sometimes 4-5 and downshifts harsh sometimes too. Why are these codes being thrown and can these effect Trans? Wheel bearings are fine aswell!? I'm kind of at loss with all this and just want to get to the bottom of this issue. Thanks!


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Loss of communication between ECM/TCM will give harsh shifts. Look at bad speed sensor on top of TCM or that same plug being broken.

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[Devon]

Ok, didn't know there was a speed sensor on top of the TCM. Anywhere else I can look for issues?


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[BigDMax05]

I think he means the speed sensor on top of the t-case. This sensor will cause all kinda of fits. They are not dreadful expensive so just change it out and make sure it is screwed down all the way. If that's not it you may have to look at the front wheel bearings. I've had a bad one that was bearing wise fine but had a tooth or two missing off the reluctor gear an it was screwed. Tried replacing the sensor and it didn't work. Good luck!

 

[Devon]

Did these sensors make your Trans shift hard at all? Reason I ask is because it almost fees more transfer case related. I will check the sensor tomorow a.m and grab one from the dealer anyways. Just to eliminate any issues.


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[maine04max]

NAPA stocks the sensor

 

[Mike L.]

I don't think it's your sensor.

 

[Devon]

What do you think Mike? Mechanical issue?


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[Mike L.]

What do you think Mike? Mechanical issue?


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Electrical problem. Youneed to take it to a dealer.

 

[Devon]

Ok thank you I will try that


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[BigDMax05]

Did these sensors make your Trans shift hard at all? Reason I ask is because it almost fees more transfer case related. I will check the sensor tomorow a.m and grab one from the dealer anyways. Just to eliminate any issues.


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Yes it did and it also went shift range inhibited. I actually ended up having two compounding problems that made it seem like 1 big problem. It all started with a code for the pass wheel speed sensor that went bad(tried a new sensor didn't work) , also about the same time I got a shift range inhibited indicator. I disassembled the valve body and thoroughly cleaned it and then reassembled it and put it back together and to no avail still Sri. Wound up changing front wheel hub and also the speed sensor in tcase (after alot of mistrial)and it solved the problems. Transmission was acting very wierd while this was going on. Clunking when it downshifted from 2-1 and harsh up shifting.

 

[MaxPF]

Problem is, he is getting codes for BOTH wheel sensors (L & R). The odds of both going tits-up at the same time is highly unlikely. Then there is the U1000. Mike is right - it's an electrical issue. Maybe the class 2 data line is fubared somewhere along the way (bad connector maybe ?)? Maybe the ABS module isn't getting power (check fuses)? These trucks have more wiring than a 787, and almost as much as a Nissan truck.....

Other than that, :nothingtoadd:

 

[battlegraduate09]

iv had a u1000 for months. I cant figure it out. Did you scan other modules ? id bout garuantee that its in every module, especially if its a hard failure

 

[BigDMax05]

Just looked at my old thread over at dp and I was getting a u1300 (class 2 data short circuit)with my problems also. You guys are most likely correct as both front wss's bad would be unlikely. This may sound silly but check all of yours fuses also. Check the big fuse (40 or 60 amp) for the abs module also.

 

[Devon]

Ok, thanks for all of the collective information. Will be checking the fuses out today.


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[battlegraduate09]

Just looked at my old thread over at dp and I was getting a u1300 (class 2 data short circuit)with my problems also. You guys are most likely correct as both front wss's bad would be unlikely. This may sound silly but check all of yours fuses also. Check the big fuse (40 or 60 amp) for the abs module also.

the u1300 is not the cause of the problem though, just a dtc set and can be retrieved with a history status.

im almost positive this is not a fuse problem, the class 2 wire is bad somewhere. iv been through this before.

 

[BigDMax05]

the u1300 is not the cause of the problem though, just a dtc set and can be retrieved with a history status.

im almost positive this is not a fuse problem, the class 2 wire is bad somewhere. iv been through this before.

Ok I am just trying to give him some ideas before he spends $1k at the dealership.

 

[Devon]

What exactly is the class 2 wire? I'm sure the u1000 is not the problem. I scanned the truck today with a different scanner and only got the front left wheel speed sensor this time. I just want my Trans and abs to stop acting up. Making for a not so fun driving experience.


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[battlegraduate09]

class 2 data line, it connects modules in a star configuration. From what i found in my past issues is the u1000 tells you the problem occured when the ignition is on, you can use a flow chart with a tech 2 to narrow down where your problem is. Different modules you can isolate and test individually. and it would be worth it to pay the dealership to do this for youf if you have to, i had my ecm wiped clean and had to pay for it out of pocket.

I can send you a flow chart that WILL point you to your problem, if your vehicle can keep communication and the tech 2 can read the modules.

 

[Devon]

Ok well, I finally got ahold of the PO an said that in one of the front wheels the sensor wires rubbed through? Would this cause problems with the Trans at all?



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