Junkyard Engine Computer Issues

Try Ebay first. I bought a Honda Accord PCM for 29 bucks.

i got a better idea as an anti-theft device when you gotta drive somewhere take the cry-seller car along. Hek if that gets stolden, abused, or coaght on fire, thats ok its right where it belongs. =

-- johnin

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Update on this. I searched for compatible engine computers online:

and found 10 or so. There was a huge variation in price, from $500 to $65, I ordered the $65 unit from All West Coast Auto Wrecking in Washington.

They sent me the wrong part, a transmission computer. Easy mistake to make, that one is on the right fender, the correct part is mounted on the left fender. I figured I'd get the run around, but they said they had the right part, and just send back the wrong one, which I did. I expected it to take a week for them to receive my package and send me the correct part, but they shipped without waiting so I got it in 3 days.

I plugged it in, and it fixed the problem. So I guess I still have to buy one from the dealer with the correct VIN programmed, but I can take my time and won't have to pay a fortune for troubleshooting and having the wrong parts replaced. In fact, I may take a crack at the bad computer. I'm an electronic tech by trade, if I can get the potting compound off I may be able to troubleshoot it. I suspect a voltage regulator, since the problem affected all parts of the computer.

Oh, I should mention that in searching the net, I found that a lot of people with a similar problem had fixed it by reflowing the solder on the instrument cluster connectors. There was a ground that tended to crack on the 1996-2000 minivans. Their van would suddenly quit and refuse to start, and they could get it going by pounding on the dash. So I pulled the instrument cluster, but could see no fractured solder joints. I reflowed the solder on the cable connectors anyway, but it didn't help in my case.

Hope this helps someone down the road with one of these problems.

-Paul

That's a good tip, I can see you know your stuff. I tried that already, I found some info online that said the solder joints on the connectors can crack, so I was in there pushing on everything thru the potting compound while my wife worked the key. Didn't make any difference.

Something is drawing a lot more current than on the good computer, though, so I have a chance of zeroing in on it. Most likely it is one of the devices connected to the "silver towers", which are heat sinks. The parts that get hot are mounted on them, so they're the ones that tend to fail, and they're most likely voltage regulators. Peering thru the amber potting compound, the one at lower left looks like a switching power supply, it probably makes 5V out of 12V.

Thanks for the reply.

-Paul

Well, why would you get another one with your vin encoded in it? The one you have is working, so it would seem pretty stupid to spend the money on one to get the vin encoded on it? Especially since your vehicle is no longer under warranty.

I'm in California. I'm told it won't pass my biannual smog test which is all computerized to prevent fraud. The car's a giant paperweight if it won't pass the smog test.

I'm going to try to fix the old one, since I'm an electronic tech. Meantime, I can drive about a year until the next smog test is due.

I'm actually pretty happy to have it driveable again, and know for certain what the problem is. I pictured getting ripped off for thousands of dollars as the dealer changed part after part.

-Paul

I'm in Arizona and have to go for emissions every few years also. The only thing they are worried about with the computer, is that they can plug in the scanner to prove there are no engine codes.

I'll check into it, but I think they pull the VIN from the car's computer. We got a stricter smog test just in the last couple of years, which now includes a sort of dyno test.

-Paul

Why would they bother with a switching power supply just to drop 12 volts to 5 volts? Reduce heat? Wouldn't a voltage divider or a regulator do the same? I'm trying to remember why these were used on computers, to reduce weight and heat, but on a car, that increases complexity unnecessarily? So anyway the VIN is encoded into the PCM, the EEPROM? Can you ask your department of motor vehicles what they suggest since this must be somewhat a common problem in repairing cars? Or only the dealer can resolve this with reprogramming the PCM, actually, the EEPROM? Unless it's just an EPROM. I found dental tools were good for dealing with potted plants.

There are several reasons- a simple series regulator would waste more than half of the wattage- with the engine running and the alternator putting out 14V, it would waste almost two thirds of the power consumed (9/14ths), converting that to heat. Then you've got reliability problems. Switchers are very efficient. A mechanical analog is a reduction gear. You could say, "why have compound low on a 4WD? Can't you just slip the clutch?" Yeah, you could...

Good idea. I removed some big chunks, but this is hard work. I wonder if paint stripper or something would dissolve that stuff?

-Paul

A paint stripper will, but not the liquid kind. Get a heat gun. Use it carefully. It makes that epoxy get jelly like while it's hot.

I've got one of those. I'll give it a try.

-Paul

Nope, tried it, got it hot enough to stink but it's there's no difference. I even tried heating up a chunk I'd pulled out so I could really tell. Didn't soften it. I'll have to see if I can get some strong solvents. Alcohol and paint thinner had no effect.

-Paul