Comm Issue

Paul Owner/Technician West Collingswood, New Jersey Posted   Latest   Edited  
Question
Programming
2010 Chevrolet Camaro LS 3.6L (V LLT) 6-spd (6L50)—2G1FB1EV2A9164140
U0073 - Control Module Communication Bus "A" Off
U0101 - Lost Communication with TCM
P0700 - Transmission Control System (MIL Request),
P2544 - Torque Management Request Input Signal "A"
Limp Mode Intermittently

Hi guys need help. Intermittent issue with car ECM, TCM, ABS, BCM and TPMS has comm codes and vehicle goes into limp mode intermittently​. ​We checked the trans vent it has been moved over to the right side as per tsb and trans fluid is not milky but smell slight burnt and brown color​. ​

Please shed some light on this issue if anyone run into it. Vehicle acted up 1 time in 3 days of driving. MIL came on and went in limp mode all the comm codes came back​.​ Was able to comm with all the module. Cycle the key on and off, everything was back to normal. 

Spoke with customer he said he had it at dealer they kept it for 3 weeks no answer​. ​TCM was recomeneded So we replaced the TCM from GM​. ​Called RAP to remotely program it. They called said it does not take program it fails in the middle of the programing and comm code is back​.​ Sure enough we could not comm with TCM. We load test the power and gnd. No problem found​.​ CAN signal ok. we plug original TCM and could comm with it​. So we thought something wrong with TCM. We install another TCM and hook scan tool was able to comm and only code it had was module not programmed and upon programming same thing again. 

I checked to see any after market add on to this vehicle none found​.​ Only thing I see is amp and sub woofer in trunk but factory radio. At this time we are lost. I don't understand is there a problem with this car or these RAP guys doing something wrong causing the programing to crash and killing these TCM's. CAN bus at DLC 2.4v High and 2.0v Low .with ESP module disconnected it's at 2.02v H and 1.95v L. Resistance at DLC 52.8 ohms and ESP disconnected 104 ohms. 

I know it's not perfect reading but is it normal to have this reading​.​ Please help

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Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
 

You need to reinstall the original TCM or TECHM. Then you need to connect a scope to pins 6 an 14 and drive it till it acts up. I have had cars with intermittent comm problems that I have driven for weeks until they acted up. Once they acted up it was easy to find. Until you can see what's happening to the network on the scope your throwing $20 bills out the window. Seriously man I would put…

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Ken Owner/Technician
Phoenix, Arizona
Ken Default
 

if you have a 4 channel scope dlc pins 6 and 14....and the can lines on the TCM . all 4 channels should mirror each other exactly...Caleb is totally correct in putting it all back together and start over...find your problem

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
 

I agree with what Caleb and Ken said. Plus, please put spaces after your periods and break your long posts into paragraphs. As your posts are they are too hard to read and you are missing out on help because a lot of people won't read hard to read posts.

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Mark Diagnostician
Elk Grove, California
Mark Default
 

U0073- Control module comm bus "a" off U0101- Lost comm with tcm P0700 - Tcm requested mil P2544 - Trans torque requested ckt Hi guys need help. Intermittent issue with car ecm , tcm, abs, bcm and tpms. Vehicle has comm codes and vehicle goes into limp mode intermittently​. ​We check the trans vent it has been moved over to the right side as per tsb and trans fluid is not milky. Trans…

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Mark Diagnostician
Elk Grove, California
Mark Default
 

"CAN bus at DLC 2.4v High and 2.0v Low. With ESP module disconnected it's at 2.02v H and 1.95v L. resistance at DLC 52.8 ohms, and ESP disconnected 104 ohms. I know it's not perfect reading but is it normal to have this reading​." This seems pretty far off to me. CAN+ should never be below 2.5V and read about 2.7V on a quality DVOM. Where are you taking the measurements at? If it has onstar I…

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Martin Instructor
Burnaby, British Columbia
Martin Default
   

Paul. First off, figure our the DTC hierarchy so that you can home in on the underlying issue. In other words, forget about DTCs that set because of other conditions. So, forget about P0700 and P2544, because they are informational DTCs that set due to the communication issue. U0073 is set in the ECM for communication Bus "A" off and U0101 is set in the ECM turning the MIL on. Looking at your…

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Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
 

Get this thing figured out yet??

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Martin Instructor
Burnaby, British Columbia
Martin Default
 

I was just wondering the same Caleb. It would be nice to see closure on help requests as soon as a diagnosis and repair has been completed, for the benefit of others in similar situations searching for assistance/direction.

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