Lance Coburn

Hello everyone,
I am working on a customer's 2004 suburban 1500 5.3 220k miles. He rolled the pickup about 20k miles ago and had problems with the vehicle going into limp mode. He changes the ecm and it fixed it for a bit. He hit a bump and the vehicle went into limp mode two weeks ago. After one more bump (dirt roads, not maintained, very rough) it died. This is the status I received the vehicle in. The vehicle currently Will not crank or start. I reprogrammed the pass lock, checked every really and can make the motor crank by powering the trigger side of the start relay with my power probe three in the under hood fuse compartment. I checked all batter cables, cleaned all negative and positive battery wires. Jumped the neutral safety switch on the trans mission and no change. I noticed a few wierd things as well. *Gets wild here* the door fab doesn't work, the doors don't unlock or lock with keys on, the dash lights flicker, and the radio doesn't stay on with the doors shut and key put of ignition, and the anti theft light stays on all the time, HOWEVER, if I remove the Ign 5 fuse from the under hood compartment, all these components work as they should. Radio stays on with door shut key out of ignition, door locks work with no key in ignition, key fab works, anti theft behaves as it should, etc. Is this a body control module problem? Is the new ecm still at fault.? He has a wrecked 2004 Tahoe, would I be able to swap in it's bcm? I'm in desperate need for some answers. Thank you so much in advance. All fuses good and relays as well. Removal of this fuse does not fix no start no crank problem. Attached is the phot of underhood compartment and the relay that, when removed, makes all things work as it should. Still no crank no start. Also, my snap on modius does not communicate with the vehicle.

BROOKLYN ARES

did you fix it yet mines did that it was ground wires for the coil packs it was fine for almost two years. Now when it rains the check engine light flashes goes in limp mode but when there's no precipitation its fine no issues.

MitchM

the fact that it had weird problems affecting a lot of electric functions suggests to me it's an electrical problem not a fuel delivery system component.

were there any diagnostic P codes stored in freeze frame memory ?

if it won't start at all, I guess you cannot check for proper signal voltages coming into the fuel tank pump and from fuel tank pressure sensor which send signal to the p c m power control module which signals how much fuel to send into each injector and when . no proper p c m signal, fuel starvation to 1 or more cylinders.

check out south main auto 's posts on you tube . he is a brilliant mechanic at diagnosing weird problems. let us know what you find ?

2004Suburban

I've been having a no-crank, no-start problem intermittently for months. Saw two videos that linked this to a bad underhood electrical center fuse block internal failure.

Here's a link to one of them:
He was able to trace the problem because his failure went from intermittent to permanent. Hope this helps.