M1097a2 trans light stays on, turns off when I give it throttle

[Chazrilla]

Starts and idles good. Limps. No Codes. Steady light while idling but turns off and blinks a little bit randomly when even light throttle is applied. Looked at the alternator and regulator. The Voltage output does not change when throttle is applied. If anyone has a thought or experience with fixing this particular fault please LMK, thanks.

 

[Chazrilla]

ok its fixed, some knuckle head used the jump cables wrong to start it and burned up the TCM chip. Had a big burn mark on it. Apparently when your trans light starts doing wonky stuff the TCM is usually the culprit.

 

[Action]

ok its fixed, some knuckle head used the jump cables wrong to start it and burned up the TCM chip. Had a big burn mark on it. Apparently when your trans light starts doing wonky stuff the TCM is usually the culprit.

So...you watched someone incorrectly jump start your truck? Or just grabbing ideas?

 

[Chazrilla]

So...you watched someone incorrectly jump start your truck? Or just grabbing ideas?

its a common issue on this particular system when someone uses an incorrect jump start procedure. They are supposed to leave the cables hooked up without the jumping truck running for 10 minutes then disconnect and attempt to start. Instead they hook it up while the jump vehicle is running and start the dead one right away. Also the chip in the TCM is designed for 1 amp but the shift solenoids draw 3 amps burning up the chip over time.

 

[springer1981]

its a common issue on this particular system when someone uses an incorrect jump start procedure. They are supposed to leave the cables hooked up without the jumping truck running for 10 minutes then disconnect and attempt to start. Instead they hook it up while the jump vehicle is running and start the dead one right away. Also the chip in the TCM is designed for 1 amp but the shift solenoids draw 3 amps burning up the chip over time.

I don't know what the official procedure is for jump starting but that makes no sense and would not effect the TCU from a purely technical aspect. More likely the TCU just plain failed or was abused in some other way. That TCU is just a typical GM TCU for a 4L80 transmission enclosed in a water tight box.

I don't have any specific knowledge on the design of the TCU but I doubt GM has something drawing 3 amps from a circuit designed for 1 amp.

I'm glad you found the cause and I hope it's an easy fix for you.

 

[Mullaney]

Starts and idles good. Limps. No Codes. Steady light while idling but turns off and blinks a little bit randomly when even light throttle is applied. Looked at the alternator and regulator. The Voltage output does not change when throttle is applied. If anyone has a thought or experience with fixing this particular fault please LMK, thanks.

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And when I saw this question, I had no decent answer of offer up... Noticed though that you appeared new to the group. Also seems that maybe you have more trucks to play with than the rest of us.

So, better late than never... Officially we Welcome you to the Outfit!

Glad the guys were able to come up with some possibilities to sling your way too.

I have a M1088 and a M1089 and the 88 has been "spastic" in the cranking department since the batteries were stolen shortly after I got the truck. Couldn't honestly say that since it was less than two weeks since it arrived that the criminal element heisted my batteries that I don't know if the truck was ever right.

ANYWAY, what I was getting around to saying is that if that were the case - only jump the truck with the "juice donor" not running - mine would be dead. Until I got it wired up right (that was a nightmare) and new batteries AND cranking it weekly and going for about a 20 mile trip, it had low battery problems more often than not. The front 12v of the pair was almost always low. Cheating the system and using a wire too small between batteries was my culprit.

So, welcome again to the group!

 

[m1161]

Starts and idles good. Limps. No Codes. Steady light while idling but turns off and blinks a little bit randomly when even light throttle is applied. Looked at the alternator and regulator. The Voltage output does not change when throttle is applied. If anyone has a thought or experience with fixing this particular fault please LMK, thanks.

I saw on YouTube a fellow who disconnects the xmsn controller plug and shorts pin A to pin E. Started the engine. At that point he started getting codes that, using a table, tells you what problems you're having.
Good luck,
'Larry, M1161