Hey all, newb here hoping someone can help! My 03 LB7 Silverado has gone whacky, been parked for about a month, fired it up, hooked up my trailer and loaded up some trash. Next morning the batteries were dead, I could hear the chime going off inside like the key was on even though it was in my pocket. Not enough juice to unlock the door.. I charged the batteries and headed to the dump, truck had no power and acted like it wasn't shifting so I pulled over to shut it down and let it reboot. When I turned off the key it kept running, gauges and radio would turn off but not the engine (service engine soon light stays on also). Came home and had to unplug the Ignition relay to shut it down. Seems to have only 4th gear, no reverse.When it's running and I turn off the key the engine stumbles like it wants to die but come right back to life. I started pulling connectors and found the C107 connector will kill the engine and the "Service engine Soon" light. I think something downstream of the C107 connector is feeding power back into the truck. Any ideas?
Major LB7 troubles
- Thread starter Diesel Joe
- Start date
I know alot about these trucks but based on your explanation the only suggestion I have would be a really bad bcm or a bricked ecm
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I don't know why it happened over night. It was fine the day before I backed the truck and trailer up and shut it off, next morning wouldn't start..
Also. You say service engine soon light. 03 is an engine symbol. 2001-2 had the words
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Possibly the ignition switch
2004 Silverado Cali lb7, Airdog ll 165, fresh sticks at 325k, Rick Fletes Dsp 5 on v2, 33x12.5 nitto at on 20 inch American Racing 20x10 wheels, Stage 5 Built Transmission by Mike Cole with triple disc billet low stall converter, 4 inch Injen cold air intake, Profab Intake Horn, Batmo Wheel, PPE Race Valve, Full EGR Removed w/ fed belt, 3.5 inch MBRP Downpipe, Full five inch MBRP Exhaust axle dump, lbz cp3 pump, Dual Platinum AGM Duralast, High Output Alternator, Cognito Pittman and idler w/ support kit, Cognito Upper Contol arms, Drilled and Slotted Rotors on all four Corners, FED Y Bridge, Shantz Custom Fab Traction Bars.
2004 Silverado Cali lb7, Airdog ll 165, fresh sticks at 325k, Rick Fletes Dsp 5 on v2, 33x12.5 nitto at on 20 inch American Racing 20x10 wheels, Stage 5 Built Transmission by Mike Cole with triple disc billet low stall converter, 4 inch Injen cold air intake, Profab Intake Horn, Batmo Wheel, PPE Race Valve, Full EGR Removed w/ fed belt, 3.5 inch MBRP Downpipe, Full five inch MBRP Exhaust axle dump, lbz cp3 pump, Dual Platinum AGM Duralast, High Output Alternator, Cognito Pittman and idler w/ support kit, Cognito Upper Contol arms, Drilled and Slotted Rotors on all four Corners, FED Y Bridge, Shantz Custom Fab Traction Bars.
I have disconnected the ignition switch, still the same.When I connect a negative battery cable to battery the ignition relay engages with key off (and ignition switch disconnected). I have connected my remote start button between neg cable and battery so I can try to trace this down. I am going to disconnect each control module (ECM, BCM, TCM, NSBU) one by one to see if I can find the culprit.. Am I forgetting any modules that may need eliminated?
The worst part is I've injured my back taking the trailer off because it won't go into reverse! going to be slow going.
feel the glow plug control module on the driver side of the engine at the very back. they relay likes to go bad back there which shorts to power, it will be very hot. when it does, it back feeds power back into the fuse block and ecm and this happens. good test is to leave the truck running with the key out like its suppose to be off, then pull the power lead to the glow plug module. if the truck dies, you know the issue.
Awsome info James, that would make sense because the issue seems to be downstream of C107. I will let you know if that's it.
Removed the power lead to glow plug relay, it is no longer feeding power to fuse block, now what? Can I drive without the relay power? Where is the best place to get one? Thanks, your the man!
so did it fix it?
yes you can drive without one, you just will have codes. they are 100 bucks from the dealer IIRC.
Yes sir it is running, trans is shifting all is well except ses light. For a cali module Napa want $300 w/ shipping! Thanks again, you saved me hours of frustration. Now to find a cheaper module.
Good to hear.
this is more of a "blind squirrel finds a nut every once and a while" type thing but its a fairly common issue ive found. My personal truck did it years ago and had a few other trucks do it since then. i jsut happen to be fumbling around under the hood of the truck while i was looking for the issue and felt how damn hot that controller was. undid it and problem solved. i was quite ecstatic cause i was thinking down the same lines you were OP
this is more of a "blind squirrel finds a nut every once and a while" type thing but its a fairly common issue ive found. My personal truck did it years ago and had a few other trucks do it since then. i jsut happen to be fumbling around under the hood of the truck while i was looking for the issue and felt how damn hot that controller was. undid it and problem solved. i was quite ecstatic cause i was thinking down the same lines you were OP
