98 Grand Voyager 3.3l PCM Troubleshooting

My 98 Grand Voyager 3.3l V6 suddenly runs rough and dies. It had been very reliable until now. I drove it up into the hills on Saturday and parked, so it got hot (but didn't overheat.) Sunday I drove up a steep rough gravel road, so it got hot, a little dusty, and the front scraped a bit as I slowly navigated potholes. It started and ran fine after all of this, then sat for a day, and when started the next morning it ran rough and died.

With the key on, engine off, I noticed a lot of clicking coming from the ASD relay and fuel pump relay.

I tried to get codes out of it using the key method, and maybe I got a

  1. Hard to tell, because the dash indicators were behaving erratically.

Although it cranked well, I cleaned the battery terminals and charged the battery. At first the digital Odo and other dash instruments were dead, though the MIL and other lights up above were working. It also wouldn't crank. Some screwing around reconnecting the battery and turning the key eventually got those things back to square one, it would crank and start, but run rough and die. Charging the battery seemed to lessen the amount of relay clicking with key on, engine off. During the few seconds I can get it to run, the voltage at the battery goes to 14V, so I think the alternator/regulator are OK.

I tried reseating the power distribution and PCM connectors and spraying them with contact cleaner, also checked all the engine compartment fuses. No joy, it was back into the situation where it wouldn't crank. I bought a cheap code reader, but that reads no codes. At some point it suddenly started cranking again, and I was able to start it and run it for a few seconds before it died, still no codes from the reader. It displays an "E", which I assume means error, and the code for "no codes".

I'm an electronic tech by trade, so I've studied the schematics in my Haynes manual and read as much on the net as I can about the functioning of the PCM. If I could get a schematic for that it would really help.

Since the relays are malfunctioning with the key on, engine off I'm guessing this isn't a problem with the cam or crankshaft sensors. I'm thinking either the PCM is bad or something is loading it, or a bad ground somewhere.

I'd appreciate any troubleshooting suggestions.

-Paul

Reply to
carbide
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check all your battery cables carefully as well as the connections to the starter from the battery. Also load testing the battery would be wise.

Ted

Reply to
Ted Mittelstaedt

The cables look good- the wire is not corroded or swollen- I cleaned the connections, the battery voltage measures good, and it cranks great. It has problems with the key on, engine off (ASD and fuel pump relays clicking randomly), when the draw on the battery is low.

So I don't think it's the battery or the main cables.

-Paul

Reply to
carbide

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