Possible shutdown relay?

 

I'll check it out if the problem keeps happening, thanks. It's not something I was aware of. It's been 6 years since troubleshooting an electrical system on a vehicle with such relays or sensors. I've been only tinkering with old school DC electrical since buying the truck.

Two days ago I installed the cheap 4-inch fan at the PCM and the problem hasn't come back yet, engine light went away this morning. I need to drive it a longer distance tomorrow with the A/C off first to really test that theory of weak solder in the PCM when super hot. I do know that the case is significantly cooler. It is especially cooler when the A/C is on since the air from the fan bounces back to the PCM off of the A/C drier/accumulator.

 

Hey everyone, I have a new and more problematic symptom with my truck now. Since installing the fan, the truck hasn't had any issues while driving. The check engine light went off and stayed off. Now today, I went to start the truck and nothing. No interior lights, headlights, or dash lights would turn on. The only thing lit on the dash was the security light (little red dot) and this stayed on. The battery and charging system are in great shape. I have never seen that security light before, not during the gauge light check or any other time. This truck has no security or security key. It is manual windows, locks, etc. The truck did come back to life and started for my trip home after a few minutes. Security light was nowhere to be seen then. Now, the same thing except it seems dead for good. I checked and switched the ASD relay with another one as well as the fuse. Has my computer given up for good? Does anyone have any idea based on my posts?

 

I pulled the negative cable on the battery for 30 minutes and now it's back to life again. Thoughts? Thanks.

 

Okay, for this last problem the positive cable that attaches via nut/bolt for the fuse panel may have had intermittent contact. This might be because it wasn't as tight as before because I ran the fan wire from it. Still, this means that this needs to be cleaned up as well although I did two years ago. There should be no other connection that isn't shiny and clean then. I'll report back soon. I'm still curious about that darn security light though.

 

My brain dead truck is still the same. It runs good if going short distances or times but all the symptoms come back if running longer. If I pull off the negative cable for 15 minutes the truck runs great and the light clears until the next time. As soon as I get a chance, I'll open the computer up. If anything is obviously burnt like a capacitor then I have someone who will carefully solder in new pieces. If it kills the computer completely then oh well, I'll just order another one for $200 or so. Unfortunately, PCM's for my truck aren't sitting on junkyard shelves. I am a 5%er with my manual transmission.

Thankfully, the bike is ready to ride so I have an alternate vehicle available now. In the meantime, what is the process to quickly reset the darn PCM? I have tried pulling the B+ then holding the key in start position for 30 seconds (no, not turning the engine or foolishness like that). Also, clearly tried pulling the positive + negative battery terminals. It always takes 15-30 minutes or so before back to good.

 

Keep us posted. If it were me I'd be throwing parts at it by now and hoping for the best. lol, I know about proper troubleshooting, but some parts are cheap and I value my time.

 

I probably would have already opened the PCM up by now but the truck is still getting me back and forth to work. I spent lots of time checking connections/troubleshooting then focused all my free time on the bike. Now that it's rockin' I can play with the computer on the truck. Either repair or replace it but all symptoms point to this. Updates to follow.

 

[/QUOTE]Thankfully, the bike is ready to ride so I have an alternate vehicle available now. In the meantime, what is the process to quickly reset the darn PCM? I have tried pulling the B+ then holding the key in start position for 30 seconds (no, not turning the engine or foolishness like that). Also, clearly tried pulling the positive + negative battery terminals. It always takes 15-30 minutes or so before back to good.[/QUOTE]

Pulling the battery cables allows all stored electricity to slowly leech from the system(capacitors,etc). To quickly discharge and reset(reboot), disconnect cables - turn key to on position - touch cables to each other (NOT to battery) for 5 seconds. Turn off key and reconnect cables to battery. Here's what happens. By turning on key and touching cables together you are creating a complete cicuit without an external power source (the battery). Now everything electrical will be searching for power (dash lights, chimes, fuel pump,etc) and will suck the system dry in a second (probably less). Got this quite a while back from a Chrysler tech. Bought my truck new and that's the way I've been doing it.

 

Great. Thanks Deer Hunter!! The explanation makes perfect sense. I certainly don't intend to have to do this much longer but in the meantime..............