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Discussion Starter · #1 ·
Forum Fam,
I'm completely stumped. I have a 2007.5 Sierra Denali awd 6.2L, been a fine running truck only 118k miles on the clock. Couple weeks ago I went to start my truck and interior lights came on, all body functions work, radio etc, etc but no crank. It's a new battery and fully charged. I pulled the inner fender, I've got power at my starter via the battery cable. However am NOT getting power to the pink wire via the relay.

I can jump the starter relay and the truck turns over but does not start. I don't believe Im getting any power to the relay from the yellow wire from the ECM (pin 86).

I thought maybe ignition switch, but when I turn key to start position, everything else shuts off like it should. I know there is a park neutral switch in the Tranny as well, but idk.

When this problem started, I also noticed a random "service airbag" light on my dash. I know it's electrical but it had me stumped so I had it towed to a shop with a full scanner, they spent a week and they are stumped, I then towed it to a different shop and haven't heard anything.

i only get the engine lock indicator and the seatbelt indicator when key is turned on (engine lock quickly goes off after a second or two), but I thought I remembered all the lights on the dash coming on when key was in on position (or maybe it's start I can't remember)

Maybe a bad ecm? I just don't know what to do. Any ideas?
Schematic Rectangle Map Parallel Floor plan
 

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Take a pair of jumper cables and bypass the existing battery cables. Just clamp onto the terminals at the top and then where they terminate. Then post back.
 

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Discussion Starter · #3 ·
Take a pair of jumper cables and bypass the existing battery cables. Just clamp onto the terminals at the top and then where they terminate. Then post back.
I will try that tomorrow. But I'm getting power to the fuse block, and everything else, and when I jump the starter relay the truck cranks just fine (but doesn't fire). I would think that would cover that, but I will definitely try. I'm out of ideas. Tempted to just order a new ECU as well, but it looks like a couple weeks for all of the dealers that sell them preprogrammed.

Has me so frustrated tempting to buy a full scanner, that can read voltages and all of the ECM/BCM/TCM sensors
 

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After that pull and inspect your fuse box. I had a melted fuse holder in mine. Also check you engine grounds and the body grounds under the drivers side door.
 
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