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Po894 TCM Location

Sierra4l80

By Sierra4l80
in Ask A GM Technician

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Sierra4l80 New Member

Sierra4l80

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2006 Sierra 2500hd 2wd wt, 6.0/4l80e. Po894 code. Fully rebuilt trans and replaced all valves/solenoids/bushings that can cause this code, tcc still has 150-200 rpm of slip at full lockup. Beginning to think it’s a connection issue. Going to start testing but literally cannot locate the tcm on this truck. Looking up replacements shows a small silver box and I know on the duramax the tcm is located on the radiator shroud. The only modules I can find are the ecu under the battery and the throttle module on the firewall. Is the tcm integrated with the pcm on this model? What am I missing here? Thanks 

Jsdirt Senior Enthusiast

Jsdirt

Posted
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Yes, the TCM is internal to the PCM. Was the torque converter replaced (I hope)?

 

This vid might help with troubleshooting.

 

 

 

Sierra4l80 New Member

Sierra4l80

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On 8/21/2023 at 12:00 PM, Jsdirt said:

Yes, the TCM is internal to the PCM. Was the torque converter replaced (I hope)?

 

This vid might help with troubleshooting.

 

 

 

Thank for your response, I was going crazy looking for a separate tcm. I’ve pretty much scoured the internet looking for fixes for this for the past month. At this point im convinced it has to be electrical. I actually tried 2 converters thinking the rebuilt one I bought might have been a dud. It doesn’t throw any other codes. I took the computer out and cleaned all of the connections to no avail so im starting to think there’s an issue in the wiring where the tcc pwm is getting just enough power to not throw a code but also not enough to get a full lockup. I’m at loss at this point man the trans has been out twice and I’ve dropped the valvebody 3 separate times so I’m grasping at straws. 

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Jsdirt Senior Enthusiast

Jsdirt

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Sorry to hear that. What a PITA! Been there a hundred times over the years with my own modern junk, and customer's. Reason #1 why I've always hated electronics in motor vehicles. It's great when it all works ... but when it doesn't, it SUCKS! 

 

The wiring on these leaves a lot to be desired, so that's a distinct possibility that there's a wiring issue. The later models are even WORSE, so be glad you have an '06. Every generation they find a lower bid on parts. It's awful. 

 

I took my '07 Silverado off the road and bought a '93 W250 with a Cummins 12v & 5-speed. At least I can fix this one without tearing every last hair out of my head! 

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