07 Cobalt No Crank! ABS/TCM/Steering Control
 

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A few weeks ago one morning the car wouldn’t start. No crank no nothing, silence when I turned the key to run. The dash didn’t display the CEL when in power only position, but did suddenly say “service air bag”. After a few seconds of sitting with the key turned to power only, the dash came back (and the CEL as it’s supposed to) and then when the key was turned to run it started up fine, no CEL, no service air bag notice. This has happened almost every day since, but only after the car has been sitting for a night or longer, so I scanned for codes and found the two codes above.

Today I really dove into the forums and found a few possible fixes which I tired. I grounded the TCM to the frame above the strut, checked all TCM and ECM connectors and pins for oil from the oil pressure sensor leak I had, checked related fuses in the main fuse box, checked both BCM connectors and pins, checked related fuses on the BCM, removed and cleaned the grounds on the front of the transmission, behind the fuse box, below the coolant reservoir tank (what a pain in the ass), below the driver side headlight (what an even bigger pain in the ass), above the driver side headlight, and cleaned out an unknown circular connector with a lot of pins and two rectangular slots on the front center of the transmission. I had a leaking oil pressure sensor which I replaced a few days ago, that circular connector was pretty oily before I cleaned it from the old leak. No other electrical connectors seem to have been reached by the oil leak.

Sadly, all that did not seem to fix it.. The car did start, but not until a few tries and again letting it sit with the key in the power position for a bit. Some days it won’t start at all! I’d really appreciate help, maybe the wiring diagrams of the modules from the codes if someone can find them? I know for fact it’s electrical, and not a bad TCM/BCM, probably a short or bad ground somewhere, but right now I’m swinging in the dark without a real idea of where the likely culprit is.

Heres to hoping I can save her, just replaced the whole front end, evap system, and god knows how many other things in the past year!