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I have a 2011 Sierra with the 4.3 automatic. I started getting a U0101 error which indicates failure to communicate with TCM. I have several symptoms that indicate the same thing, transmisison in limp mode, missing gear selector indicator on dash, stabilitrak and traction control warnings, etc. So the code lines up with the problem.
I swapped out the TCM for a refurbished one that was programmed to my VIN. I now have the exact same problem. I am wondering if there is a chart somewhere that has the correct voltages listed for the TCM harness with the ignition in the "on" position. I measured them to see if there was an indication of a bad wiring connection and I've listed the readings in the attached pdf.
there were no readings on pins 16, 17, 23, 30, 35, 40, 41, 46 - no voltages nor continuity present to ground.
and help available would be greatly appreciated.
Attachments:
Last edit: 5 months 3 days ago by timothy.mccollum.
Hopefully this is the correct wiring diagram, but having that many dead pins is a big red flag.
Check both power feeds Fuses 14 ( Hot at ALL Times) and Fuse 19 ( Hot with Run/Crank relay energised).
Confirm you have a good ground at G106 which also has other circuits and a splice. Could be a clue if you've no other symptoms (which would indicate might be good!).
I see you've ohmed a bunch of stuff, it is better to use a test lamp and load the circuits (KOEO) to check powers and grounds. Or use your DVOM and do Voltage drop tests.
Never stop Learning.
Last edit: 5 months 3 days ago by Paul P.. Reason: spelling
Thank you. I was able to get out and check the ground today, it is clean and there are no breaks in that wire between battery and ground connections.
I've also been able to determine that some of the null pins were because I had two sensors unplugged (not relevant to the U0101 code as I had unplugged them for diagnostic reasons). The wiring itself looks clean. It took several hours to pull it all out from the way it is routed and go over it visually. There was a lot of disintegrating plastic loom which has all been replaced by heat resistant cloth wiring tape.
At this point, the code remains and so I am still working on it.
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