TCM loss of communication

BAMA BOY 1981

MEMBER
2011 CHEVROLET TAHOE
5.3L
V8
2WD
AUTOMATIC
180,000 MILES

Having an issue with TCM failure to communicate. A few weeks ago, after the wife dropped kids off at school bus, she started noticing that it wasn’t shifting and decided to turn around and bring it back so I could see what I thought. After getting in to drive I noticed the gear indicator wasn’t working properly, then it was hard to take off going. So, that’s what had me look in the fuse box and noticed the fuse for TCM #14 was blown. So, I get another fuse that was brand new and went to replace it and it blew on contact. So short to ground is where I started looking for wires that may be rubbed or pinched causing it to short. I’ve yet to find anything but I’m not too sure on how to test it or know the wiring diagram to know what to look for. I’m at my tipping point of losing my mind. Any help would be great. Thanks

Saturday, December 11th, 2021 AT 5:10 AM

5 Replies

JACOBANDNICKOLAS

MECHANIC
110,127 POSTS

Hi,

Fuse 14 sends power directly to the TCM. Disconnect the TCM and inspect the connector for damage, pins at the connector that are bent, broken, corroded, or anything out of the norm. Check for wiring that has insulation worn or missing. Additionally, with the connector disconnected, remove the fuse and test for continuity to ground where the fuse makes contact. If the battery is connected, you will find 12v on one side and the other should have no power and no continuity to ground. If it has continuity to ground, then the power supply wire (red wire with a white tracer) is shorted to ground.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-wiring

I attached the wiring schematic related to the transmission control (TCM). Note: The TCM is internal in the transmission (see pic 5). At the rear of the transmission is a wiring harness connector. From there, wiring goes into the transmission and to the components. If nothing is found externally, we will need to drain the fluid and inspect the wiring in the transmission.

Let me know what you find.

Take care,

Joe

See pics below.

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Saturday, December 11th, 2021 AT 11:10 PM

BAMA BOY 1981

MEMBER
3 POSTS

Thanks for the response and guidance. Is there a trick to removal of the connector on back of the transmission? I’ve been able to pop the white tab up to unlock it but have been unable to rotate counterclockwise to disconnect. Okay, just wanted to make sure I’m not missing something and cause more of issue. Thanks again for the help.

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Sunday, December 12th, 2021 AT 8:58 AM

JACOBANDNICKOLAS

MECHANIC
110,127 POSTS

It sounds like you are doing it correctly. Are you pulling while turning it? I'm trying to remember if it was a 1/4 turn or if it just pulled straight off. However, it should turn as you are doing. I found a pic below showing the sleeve that holds it in place. It should turn. See pic.

Let me know if you got it.

Joe

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Sunday, December 12th, 2021 AT 3:53 PM

BAMA BOY 1981

MEMBER
3 POSTS

Thanks Joe, actually I had to take a step back from it this afternoon and figured I’d get back to it tomorrow morning. But I will get back with you on what I got and hopefully with your help I’m able to make some lead way and get this issue resolved soon. It’s definitely been a learning experience for sure.

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Sunday, December 12th, 2021 AT 7:21 PM

JACOBANDNICKOLAS