Ok here's my nightmare. Customer's car wouldnt start after sitting overnight. Turn the key on and everything is normal. If you try to start it you get nothing. I tryed a new ign switch with no luck so I put the old one back on. I also tried the lock cylinder with the pass lock on it because the key would hang up and you could partially remove the key with it on. Still nothing. It will turn over if you jump the starter terminals across but wont start. I tried a bcm and reprogrammed the passlock security system again, which takes over 30 min, and still the same symptom. Please help!
Do you have a scanner to check for codes and to check ignition switch input and out put
Does it have a remote starter?
A used BCM will not work
and a new BCM have to be programmed at the dealer
September, 9, 2010 AT 2:43 PM
No remote starter or any other aftermarket crap. Bcm doesnt have anything to do with the starting system. No codes. Ign switch is throwing all the right voltages. The problem is in the starter relay. It has b+ thru the 40 amp fuse in the power dist box and at the relay terminal. The system works like this. Ign switch sends 2 signals to the pcm, a crank signal and a crank relay signal from the pnp switch, this signal tells the pcm to ground the relay which sends the 40 amp power to the purple wire that goes to the s terminal on the starter. I have correct power to all wires except the pcm isnt grounding the wire that switches the relay. So after tripple checking all wires, one would say pcm, so I got one and had it programmed and still same symptom. I have a fellow tech that works at a gm dealer and he doesnt have an idea either. Anyone wanna give it a shot?
September, 10, 2010 AT 10:04 AM
Update: If I take the start relay out and do the work of the pcm and jump the 2 terminals together and the car cranks normally.
September, 13, 2010 AT 6:13 AM
Connect scan tool to Data Link Connector (DLC). Turn ignition on.
Select PCM DATA LIST.
Observe CRANK REQUEST parameter while turning ignition switch to START position.
May, 21, 2012 AT 4:32 AM
Aloha, I have the very same symtom, has this resolved? If, so, could you please share? Thanks.
July, 25, 2012 AT 3:07 AM
It sounds to me as if either the starter relay is bad, or the PCM is bad. If the relay is receiving the proper reference voltages and grounds, but not passing power to the starter, it's the culprit. If not, it's the PCM or a bad wire between the PCM and the relay. Check continuity.