Sunday, March 2, 2014

1997 Dodge Dakota PCM Repair

My transportation situation in 2014 has started out bad. My car decided it doesn't want to run when on pavement anymore (works fine in the driveway). I'd been two weeks trying to fix it (along with working a 50hrs/week and studying for CS50x) when my truck started stalling randomly. The first time I was pulling out of the driveway on the way to work, it cranked for a minute then started and ran fine. The second time (same day) I was driving through town on my way home from work and it just started coasting. Fortunately it re-started just as I was preparing to coast onto the shoulder. I got home and pulled the codes.

Diagnosis

  • P0320 - Crankshaft Position Sensor
  • P0351 - Ignition coil A
I know I pinched the CPS wires when I put the transmission back in, I just hadn't got around to replacing it. I searched for P0351 and it seems it's usually not the coil, but the PCM failing. I also found that there is a header in the PCM that can cause stalling problems. It's on the voltage regulator board.

I replaced the CPS and coil just to be on the safe side. Then started it up and wiggled the wires at the PCM. The center (white) connector would cause it to skip. So I pulled the PCM and re-soldered the header (see links).

Repair

What a pain that was! it's mounted to a aluminum plate that sucks the heat out of the connector. I ended up with a hot air rework gun at 300C and my soldering iron at 400C. It barely melted the solder, even after heating it for a few minutes! If I do this again I'll put it on my BGA rework pre-heater (electric griddle) and heat the whole board up!

1997 Dodge PCM Voltage Regulator Daughter Board?


Anyway, I reassembled the PCM and sprayed all the connectors with De-oxit. Wiggling the wires no longer has any effect on the engine. At least I'm (hopefully) back to one driveable vehicle. If I have to I'll try to pull the board under the potting and re-solder that too, but for now it seems to be working again.

UPDATE: It worked for a while, but started acting up again. I bought a used one off ebay and the truck has run great ever since. I pulled the main board out of the case and started cleaning the goo off it, I think it's the connectors where the harness plugs in, but that's as far as I've got.

Links

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