BCM? Possibly a fault or poor solder connection in the VTD, (Vehicle Theft Deterrent) circuits turning off the injectors. A high end scan tool would show what caused the last no start problem, (wrong key, didn't recognize key, etc). That's pretty weird, never seen that before.... first time for everything

 

Don't think it was a poor solder joint or trace fault. I removed it from the plastic box, reflowed solder on the connectors, did the usual flex test and could not get it to fail once warm. Soaked it with freeze mist, and let it sit outside for half an hour and the vehicle would not start. Interior lights, windows, door locks all seem to work normally even when it did not start.


We took the BCM out of the 2000 Blazer (same part number) did a relearn with the 1999, and it started after sitting out overnight in -27c weather. We did a relearn on the faulty one in the 2000 and it had a problem starting.


Anyway, the 1999 had a replacement BCM reflashed by the dealer and all seems well.


I saw the VTD flagged as "no" with the snap-on scanner, but did not think to watch it as we tried to start it.

 

Interesting. Almost has to be a problem with VTD somewhere in there. Those are the only circuits in the BCM that can affect engine running. Good job duplicating the condition! Now we have one more thing to consider on a cold no-start. Guess I'll bookmark this thread for future reference. Thanks for posting back, good job.