Hi Everyone I am new to this forum and GM'*. I bought a 2002 Montana.
I first changed the battery, because the old one froze. No crank. Spent countless hours searching the inet and most posts lead me to the passkeyIII reprogramming with the ignition switch. I tried this numerous times, still no crank. Found a post explaining where the starter relay is, I looked at the relay(the one next to the battery) and found the connector was partially unplugged. Plugged the relay in solid, and bam. Started up like a charm. The van is at my friends place. He started it and moved it out of his way. I went tonight to pick it up and no crank again. So of course first thing I check is the starter relay again. If I jump out the Red and Purple wires on the connector the van will start and then stall right away. I checked for 12v at the wires for the relay coil and there is indeed 12v there, when the ignition switch is in the crank, and run position. This is what is puzzling me. Even though there is 12v at the coil, the relay is not energizing. I tested the relay by connecting the terminals directly to a battery. I even tried my coolant fan relay where the starter relay goes, and that won't pull in either. I am going to try another key maybe it is the passkey locking it out. Maybe I am getting a false ground at the relay coil terminals if the PCM isn't sending the command. According to the wiring diagram it looks like the PCM switches the ground to this relay. For now I am stumped. I am an instrumentation technician by trade, working in control systems so am very familiar with control signals and relays. Please don't be afraid to get technical with me. Thanks Nick

gms use ground control for all the relays. starting then stalling seems like the security fighting you. with the relay socket make sure where all the pins plug in are tight, ive had that happen a couple times from the factory those are loose and intermittent.

Thanks JW I will try that, although I bent the relay prongs slightly in the proper direction to make contact in the connector and twisted and wiggled the relay in the connector while my buddy turned the key for me. I'll have to somehow bend the little connector ends so they make better contact, or cut the connector off and hard wire another relay in. I just didn't want to cut the connector, if this wasn't the problem.

you say you were getting the pcm'* ground signal to the coil side or not?

Yes, 12V present, in crank, run position, 0V in off position.

something is weird there shouldnt get 12v in run. if you measure the pin that goes to the pcm refrence to batt neg it should be high in run then go low when you try to start it.

Ok, so explain this one to me.

I neglected to mention that before I found the relay unplugged, and I was doing the key relearning, I had removed the 60 amp headlight fuse, under the hood. So the headlamps wouldn't drain the battery. Now without replacing the fuse, after plugging the relay in the van started. This was all prior to my original post here. So remember I said, 2 nights ago, the van would not crank. I found a post that said to try turning your headlamps on while cranking if they dimmed then there is power to your ignition circuits, due to the current draw of solenoid, starter etc.

I realized tonight when trying that, I hadn't put the fuse back in. Once I put the fuse in, I turned the key and it started no problem. So I removed the fuse again, tryed cranking and nothing. Put the fuse back in and it started again.

What would the headlamp fuse have to do with the engine cranking?

it must power something else that the engine needs, gm likes to do that, they put the primary description on the fuse but there may be other things on the circuit.

Well, hopefully this saves someone some premature baldness. Thanks for your help JW.