TCM wiring issue

1985 - Present, Questions, discussions, regarding anything related to the Humvee. (NO AUCTION or EBAY)

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jssfire
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TCM wiring issue

Post by jssfire » Sat Mar 18, 2023 5:07 pm

We had the wires cut from trans relay to tcm. I traced 4 wires from TCM over the transmission and back into the battery box.
537B went to trans relay #4 and trans power CB
599A went to ground shunt.
599C went to ground shunt.
290c went to trans relay #3.
For some reason if I leave wire 599A unhooked the truck runs fine with no trans light codes. But the rear battery runs down overnight.
If I hook it up the trans light stays on. Also the 599A wire is showing 24v when it should be a ground wire.
What am I missing. Retrieved the codes and only code I got was 63. Which didn't tell me anything.


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Ted Gates
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Location: Eaton Rapids, MI

Re: TCM wiring issue

Post by Ted Gates » Fri Mar 24, 2023 3:36 am

It's been awhile since I looked at wiring harnesses. I had a truck that ran fine but gave a 70's code but I could never solve it.

I had another that drains the rear battery if I don't disconnect the rear battery neg. I changed everything (generator, tcm, etc) but not harness, and it still does it. So my guess it's the harness and solving that insitu is not an option. So I just put in a battery disconnect and it worked great.

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