Question: lmm wont start after build

[770JOHNNYW]

just finnished a build on an lmm. went to start the truck today (after sitting for 6 months) i have power everywhere but the starter wont engage. checked everything all grounds are good and nothing seems to be left unplugged but im also unable to read any codes efi live says no vehicle found and other scanners say link error like the cig lighter fuse is blown but its not. also the p-r-n-d indcator is not showing what gear the trucks in. any clues?

 

[770JOHNNYW]

also not sure about the gm update it has moonshine tuning and also have a spare ecm...neither change anything i know vats are off in mine im sure tony turned them off in this one as well.

 

[GMC_2002_Dmax]

TCM got grounded out, no key/start, no PRNDML indicator........bad tcm would be my guess.

Swap the tcm with a known good one once you make sure no shorts exist, if you take the LMM tcm and put it in another truck and no crank/no start the problem is the tcm.

 

[770JOHNNYW]

TCM got grounded out, no key/start, no PRNDML indicator........bad tcm would be my guess.

Swap the tcm with a known good one once you make sure no shorts exist, if you take the LMM tcm and put it in another truck and no crank/no start the problem is the tcm.

Ill give it a shot....the tcm was never unplugged while it was sitting I don't know. And I still can't get anything on the obd port I checked all the fuses and found nothing still get "link error "

 

[JoshH]

TCM is my first guess too, but it could be a problem with the CAN bus since it isn't communicating with anything. Did you remove anything during the build that communicates on the CAN bus while it was apart that didn't go back on?

 

[770JOHNNYW]

Umm like what....maybe coolant level sensor and that's all that was removed. I don't know if that would cause it. Its saying service trailer brakes service traction control service brake system all flashes back to back.

 

[JoshH]

No, a coolant level sensor doesn't communicate on the CAN bus. I was thinking maybe the GPCM. I have no idea what you did or what you built the motor for. Just trying to help you get it figured out.

 

[770JOHNNYW]

No, a coolant level sensor doesn't communicate on the CAN bus. I was thinking maybe the GPCM. I have no idea what you did or what you built the motor for. Just trying to help you get it figured out.

Yea thanks man ill check the gpcm I just cant get the scanner to communicate ...its full build with mpi twins nothing crazy but I did move the alt hot wire out of the big harness in the front to clean things up but thats it.

 

[770JOHNNYW]

No, a coolant level sensor doesn't communicate on the CAN bus. I was thinking maybe the GPCM. I have no idea what you did or what you built the motor for. Just trying to help you get it figured out.

Yea thanks man ill check the gpcm I just cant get the scanner to communicate ...its full build with mpi twins nothing crazy but I did move the alt hot wire out of the big harness in the front to clean things up but thats it.

 

[770JOHNNYW]

still no communication with ecm

 

[JoshH]

Will the motor run if you jumper across the solenoid wire to make it crank?

 

[Bonestock]

Lmm

Give Trent a call. He had similiar problem with my lmm. Not sure what he did to fix?

 

[770JOHNNYW]

Will the motor run if you jumper across the solenoid wire to make it crank?

Just spin over no start can't tell if injectors are firing b/c can't read ecm

 

[JoshH]

Sounds like it might be a problem with the ECM then. I don't think a TCM problem will keep it from running, only from turning over and shifting. Maybe get a pinout diagram and make sure the ECM is getting power and ground everywhere it is supposed to.

 

[770JOHNNYW]

Sounds like it might be a problem with the ECM then. I don't think a TCM problem will keep it from running, only from turning over and shifting. Maybe get a pinout diagram and make sure the ECM is getting power and ground everywhere it is supposed to.

yea i checked that got a gm pinout says pin 1 3 and 5 should have power and they do...im letting it sit with the cables off for a while for the second time i guess we'll see. thanks

 

[JoshH]

Do you have another truck you can put the ECM in to test if you can connect to it in there? Should help you determine if it is a truck or computer problem.

 

[770JOHNNYW]

still cant get the indicator line under the p-r-n-d to come on something is strange

 

[770JOHNNYW]

Do you have another truck you can put the ECM in to test if you can connect to it in there? Should help you determine if it is a truck or computer problem.

yea i actually have a spare ecm no difference...

 

[TrentNell]

Have you double checked all the engine grounds ?

 

[770JOHNNYW]

Have you double checked all the engine grounds ?

yea man pulled them off twice i actually took extra caution to make sure they were clean and tight before i put the front end back on...triple checked