PCM keeps shorting out

1998 DODGE DAKOTA
150,000 MILES • 5.2L • V8 • 2WD • AUTOMATIC
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RYAN BALDAUF
  • MEMBER
  • 1 POST
So at first my truck wouldn't start one day. It wouldn't crank, the fuel pump wasn't engaging, but I had power to the radio and stuff. I found out my PCM was fried. I then ordered a flashed board and Installed the new one. It then fired right up with no problems but showed me a code for transmission gears second and fourth. I didn't drive it or anything at this time so I had my mechanic come to my house and change the solenoid pack to fix the code. Well after I got the check engine light to go away I thought it was good to drive. So I started it up and drove maybe three to five miles to a gas station. When I got to the gas station I shut it off and when I went to start the truck back up I had the same issue again. Where the ignition side was not working. The new board had friend on me again. I then had it towed to a mechanic that was supposed to be a family friend. He then told me the board was no good just like I told him. He wanted me to get another board so he could fix it and get it going. I got the new board in the mail brought it to him and explained that something has to be wrong that's shorting out my board and to not just start it and think it's fixed. Well that's exactly what he did. So now three boards later he tells me the boards I got were bad. So I then got O'Reillys and get a board from them and bring it to him. Well now that he has installed it he says it's showing automatic shutdown relay on his computer and can't find the issue or doesn't know where to look. I have been dealing with this for a year now and really would like to just get it figured out. I'm going to go tow it from his shop to my house and attempt to tackle this on my own. I have meters, tools, and knowledge about circuitry. I don't know where to look or where to begin to look though. I do know that before this all happened I had these following things happening from time to time -

My radio would sometimes not come on when I started the truck so I would have to shut it off and turn it back on to get it to work.

My rear stereo speaker would make a popping noise when I was driving and hitting bumps.

I had to give it gas when I started it sometimes cause it would lag a bit and the truck was fuel injected.

One morning when I went to start the truck it would click and not fire up and I would have to turn ignition all the way back and try again.

Now when the board fried I had no power to the fuel pump or gas gauge but I had power to my lights and my radio.

Any information would be so much help guys thank you!
Jan 9, 2019 at 1:19 AM
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CARADIODOC
  • ✓Experienced Mechanic
  • 34,397 POSTS
First of all, there is very likely nothing wrong with any of the Engine Computers. All of the circuits feeding it are much too well-protected to let anything external cause a failure. There is one exception related to a grounded wire feeding alternator, but I will have to refer to my notes to describe that better. If that caused an internal jumper to burn open, there's an easy way to solve that.

The engine will idle too slowly any time the battery has been disconnected. You will have to hold the accelerator pedal down 1/4" to keep it running. There's a real simple solution for that too. Drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals. That initiates the relearn of "minimum throttle". From then on, the computer will know when it must be in control of idle speed.

There won't be any diagnostic fault codes in the Engine Computer since the battery was disconnected, so the place to start is by determining if the automatic shutdown, (ASD) relay is turning on. If you don't have a scanner, use a test light to back-probe the dark green/orange wire at the ignition coil, any injector, or either smaller terminal on the back of the alternator. You should see the test light turn on for one second when you turn on the ignition switch, then it will turn off. You might hear the hum of the fuel pump at the same time. What is important is if that voltage returns when the engine is rotating, (cranking or running). If it does not return during cranking, the crankshaft position sensor and the camshaft position sensor are the main suspects. You'll need a scanner to view live data to see which signal is missing.

It sounds like you have an unrelated common starter problem. If you get a single, rather loud clunk from the starter each time you turn the ignition switch to "crank", but the starter works after cycling the ignition switch back and forth repeatedly, the contacts inside the starter solenoid are burned away. Most people just replace the entire starter, but the contacts are very inexpensive to replace separately.

The flashing heater control switches indicate memory was lost due to the battery being disconnected. You'll need to put the system into calibration mode once the other repairs are completed. I'll have to locate the instructions so I tell you the correct switches to press.
Jan 9, 2019 at 9:53 AM
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