M1097A2 Random Limp Mode

[The Wazu]

Hello all, long time no talk. My 1097A2 is in Limp mode with no trans light on. It’s got me all over this rig, checking wiring and so on. To start, I haven’t been driving this rig much due to, “life”. By the time I was able to get some time dedicated to it, the batteries were shot, squirrels made nest in the battery compartment and I noticed a power steering leak (cooler was leaking). I took the batteries out, charged them while I replaced the cooler and lines and cleaned up the battery compartment. No issues with wiring in the battery compartment. Jacked the front up and bled the system for about a day or two in intervals. Never paid attention to the trans light when I was bleeding the power steering system. Got everything bled and dry, go to drive and low and behold another issue, I can’t get over 40mph safely. My question is, could I’ve messed something up when bleeding the power steering system? I’m using two civi car batteries 24F series to power this rig. Never had issues before and they were in it when I got it, can these batteries not give the TCM enough juice? I have power to the circuit breaker and I tried to reset both the tcm and breaker, no fix. The relay I replaced about a year ago due to the trans light just being on, but now the opposite is happening. My brain is telling me it’s electrical but my gut is saying I didn’t bleed this system right causing it to be in limp mode. Fluid is all good is both systems, no bubbles and fluid is where it’s supposed to be on the sticks. Any help would be great before I start tearing into the harness tomorrow.

 

[Mogman]

Does the trans light always come on in run but not running? if so have you checked the codes?? there are codes that do not light the trans light.
If the trans light does not come on in run (without the engine running) then you probably have ether a light issue or a power issue (switched 12V) to the TCM

 

[The Wazu]

Does the trans light always come on in run but not running? if so have you checked the codes?? there could be codes that do not light the trans light.
If the trans light does not come on in run (without the engine running) then you probably have ether a light issue or a power issue (switched 12V) to the TCM

Thanks Mogman,

Trans light always came on when the ignition switch is flipped to “run”, once started it would go away. Now there is no light at all in the “run” position.

I agree there’s an electrical issue but no I have not checked the codes. Are you talking about a scan tool for the code reading or using the method of reading the trans light flashing configuration??

This morning I pulled another TCM out of a truck and plugged it in, no difference what so ever, so to me, its not getting power.

What are your thoughts on the 24F series batteries? They both have a charge, 2021 is the date code. I’m wondering if one battery isn’t working properly.

If the trans light doesn’t work, will that throw the truck into limp?

I pulled that diagnostic chart off the forums last night, before I tear into the harness today I wanted to see if there was a “simple-er” fix to this issue.

 

[The Wazu]

Fixed, bad batteries. So simple I feel bad making this whole post. Thanks for your help Mogman, much appreciated.