Trans light always on

[thompsoncustom]

after doing some reading on here I see that my trans light shouldn't always be on, was on when I got the humvee and had a code (73 I think) which I fixed but the light never went away the code just didn't flash anymore so I assumed the light was suppose to always be on.

What non-code related things keep the light from going off? Thanks

 

[Mogman]

More information.
The light is on any time the run switch is on or all the time?
So now it only flashes code 12?
The first thing I would do is unplug the J1 connector at the TCM and make sure that the TCM is what is causing the light to be on.

 

[thompsoncustom]

More information.
The light is on any time the run switch is on or all the time?
So now it only flashes code 12?
The first thing I would do is unplug the J1 connector at the TCM and make sure that the TCM is what is causing the light to be on.

Anytime the run switch is on.
Yes
Can I unplug and replug that with the batteries connected or do they have to be disconnected first?

 

[Mogman]

To disconnect and connect J1 the batteries can be connected but the run switch needs to be off.

 

[thompsoncustom]

To disconnect and connect J1 the batteries can be connected but the run switch needs to be off.

thanks for the tip. once the parts for my PCB come in and I get that back together I'll test the light without the TCM plugged in.

 

[Thunderbirds]

Anytime the run switch is on.
Yes
Can I unplug and replug that with the batteries connected or do they have to be disconnected first?

Just to clarify b/c it's not 100% clear the way you are describing:

Turn the switch to run only not starting the engine yet, the light stays on.
Start the engine and return to run, the light should be off.

 

[thompsoncustom]

Just to clarify b/c it's not 100% clear the way you are describing:

Turn the switch to run only not starting the engine yet, the light stays on.
Start the engine and return to run, the light should be off.

So turning the switch to run the light comes on, start the engine and return it to run the light never goes off until you turn the truck completely off.

 

[Retiredwarhorses]

So turning the switch to run the light comes on, start the engine and return it to run the light never goes off until you turn the truck completely off.

you’re TCM isn’t seeing the crank position sensor….meaning the TCM doesn’t see the engine running.

 

[thompsoncustom]

you’re TCM isn’t seeing the crank position sensor….meaning the TCM doesn’t see the engine running.

ok I checked the resistance at the sensor and got 147ohms not sure what it should be.

Now where does the TCM read the input from the CPS as i'm not seeing it on this picture of the J1 connector. Is that what they are calling a engine speed sensor?

 

[thompsoncustom]

More information.
The light is on any time the run switch is on or all the time?
So now it only flashes code 12?
The first thing I would do is unplug the J1 connector at the TCM and make sure that the TCM is what is causing the light to be on.

tested it today when the j1 connector is unplug there is no light at anytime.