I was driving my 2003 B2300 to work today and suddenly it just died while I was slightly accelerating up a mild incline. The lights, radio, wipers,etc were working fine. When I tried to start the engine nothing would happen. The starter wouldn't turn over and I didn't hear the solenoid click. It was hard to hear where I was, but I don't think I could hear the fuel pump come on when the key was turned on either. I checked the PCM and starter fuses and they both had continuity. Then I remembered I had an OBDLink MX+ dongle in the glove box so I plugged that in to the OBD2 port. The dongle indicated power was at the port and the app would connect with the dongle, but it could not connect to the PCM. I tried turning the key on and off several times. Then about 20 minutes after it had died, I tried to get the OBD2 Link app to connect to the PCM again and it worked. There were no DTCs. I then tried starting the engine and it fired up so I drove it another 1-2 miles in to work without any problems.

I'm going to spend some time digging through the manual today, but to me it seems like either some sort of bad connection with the PCM, the PCM got some moisture in it (it was raining) or some heat related issue with the PCM. Am I correct in assuming that the problem is most likely PCM related? Anything else I should be checking? I know that something like a bad clutch pedal sensor might keep it from starting, but it wouldn't have made it die and wouldn't have prevented me from connect the OBD2 dongle to the PCM. Thanks for any suggestions.

 

Do you remember if the CEL(Check engine light) came on with key on?
CEL on means PCM has powered up

Yes, no starter motor and no click if PCM was off, i.e. PATS couldn't work

No fuel pump either, so maybe you didn't hear it

The PCM fuse and PCM relay power the PCM, of course, but also the injectors and fuel pump relay, so if PCM relay turned off then engine would stall and wouldn't start again

Swap it with another relay in the engine fuse box, and keep an eye on the CEL

 

I did notice that the CEL light was not on when I had the key on and was attempting to connect the OBD2 dongle to the PCM.

Thanks for the info. I checked the fuse, but not the relay. I had an issue like this a few years ago where my truck would sometimes not start, but then it would sit for a while and start just fine. I replaced the fuel pump relay and that didn't happen again.

 

Yes, no CEL = no PCM

Pull out all the relays in engine fuse box(one at a time) and have a look in the slots and at the relays "tabs" for signs of corrosion

You can also pull off the 104 wire connector on the PCM and have a look at the pins and slots for signs of corrosion

Electronic contact cleaner can be sprayed on pins and in slots, to clean them, its also sold as MAF Cleaner if you already have some of that

 

Thanks. I will give that a try. I have some contact cleaner and some MAF cleaner. I had no idea they were essentially the same thing, but it makes sense.