Is there any certified GM techs in the group? U0109 is driving me insane.

[Fless]

does it have the rear air ride auto level pump? seems like I remember a youtube video on a can bus that traced back to the module back there. saying it's prone to corrosion because of the location. ended up using a jumper wire to loop the can and bypass the module to the system that had failed years before and wasn't worth fixed.

my memory is horrible these days, but seemed like it was a random no start as well.

This is probably the one you're referring to:

 

[Jmix91]

the heat soak issue makes me think it is a poor electrical connection, I would start at the fuse box now that other things have already been done
like something is expanding when hot loosing connection and then contracts after it sits and cools making contact again
same kind of thing can happen when it is cold out and then works when it warms up.

You’re on the right path lol. I notice the FPCM connector did not have power once she stalled. Now I have to find the break in the wire

 

[Jmix91]

I feel like I’m studying to be a master technician ‍

 

[Jmix91]

This is probably the one you're referring to:

I have a Z71. My høe does not have ESC.

 

[Doubeleive]

You’re on the right path lol. I notice the FPCM connector did not have power once she stalled. Now I have to find the break in the wire

it has been mentioned before that the fuse boxes can have crack's, I think that is unlikely at least on this generation. but it could be a corroded or dirty pin or one not seated right or the ecm harness/connection. if it is a just single wire to the module at least that makes finding the break a little easier

 

[j91z28d1]

an odd wiring design I've noticed on these trucks is a lot of the fuses don't have power until that thing is turned on. usually fuses have power say before a relay these are after a relay. don't know that your circuit just a thing that caught me up once trouble shooting stuff on this Gen, as I'd never. seen that before. expected a fuse to have power and it wasn't supposed to.

 

[Jmix91]

Well the FPCM didn’t have power after stalling so I chased that power wire (which is a straight shot to the fuse box). So far come to find out the fuse box wasnt seated all the way down. ‍smh. So it’s running right now just waiting to see a difference

 

[Doubeleive]

Well the FPCM didn’t have power after stalling so I chased that power wire (which is a straight shot to the fuse box). So far come to find out the fuse box wasnt seated all the way down. ‍smh. So it’s running right now just waiting to see a difference

I had mine in a body shop once and they had the front left fender off for replacement and they had to move it and it wouldn't start so I went down there and in about 3 minutes figured out that they had bumped the fuse box and it wasn't seated properly, the lights were all on like everything was normal but it wouldn't start, reseated the fuse box and problem solved.

 

[Jmix91]

I had mine in a body shop once and they had the front left fender off for replacement and they had to move it and it wouldn't start so I went down there and in about 3 minutes figured out that they had bumped the fuse box and it wasn't seated properly, the lights were all on like everything was normal but it wouldn't start, reseated the fuse box and problem solved.

That might be my problem. I’ll feel more comfortable once I get rid of the new CEL P0193. I had replaced the fuel pressure sensor like I said before and then “fixed” the stalling problem now I have a P0193

 

[Doubeleive]

That might be my problem. I’ll feel more comfortable once I get rid of the new CEL P0193. I had replaced the fuel pressure sensor like I said before and then “fixed” the stalling problem now I have a P0193

connect a fuel pressure tester on the rail and see if it is actually high or not, that should point you one way or another.