Thread: Bad PCM?

Ok, so my car is possessed. Started the other day on a very rare occasion while cruising, and is now more frequent and seems to effect more. At first I noticed my stereo, lights, etc would turn off for a second or two and then turn back on. The times it did this seems random and far apart, i cannot find any pattern to replicate it. At first I thought it was my stereo causing it but I have since ruled that out. Most recently I was driving at a steady speed and the lights and everything turned off, horn blared, wipers and fluid switched on, TCS turned off, and my fog lights turned on that I noticed. TCS and fog lights stayed on after everything returned after the moment of insanity but did turn off again when I switched them back on/off.

I tried to figure out any pattern or way to replicate. Wiggled everything I could think of in the engine bay/fuse boxes. This does appear to happen after being driven a while, but it is random so I can't be sure yet. One thing I should mention is I had removed the top half of my air box to put a cone filter on the end of my MAF, and had a flat peice of tin sitting between the filter and PCM so it wouldn't burn up my filter. Maybe now that it's been 30*c a lot around here again it started getting hotter and burned up the PCM causing a short or glitch of some sort. I have moved the filter to outside the box and removed the tin peice. Maybe that was the cause and a need a new computer?

Has anybody had a similar occurrence or ideas for what to check from here?


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PCM doesnt control fuctions like fog lights, horns, radio's, wipers etc etc, thats a body control function.

I highly doubt that you building an intake did anything. Unhook the battery and remove all known body grounds and battery grounds and clean them, it's a simple thing that could help and then wait to see what happens.

My PCM sits on the cars metal frame for many years now and has never shorted or anything.

I thought the tin could have kept heat in and done damage. When I was checking everything to do with the stereo I had the battery unhooked and there doesn't seem to be any loose wires anywhere that i can tell. Is there some module that controls these functions? It seems to cut everything out, including making the car bog down for the moment this happens (then it recovers).


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At first I had thought it to be my stereo sending a short through the fuse box or something (aftermarket). But it doesn't blow fuses or fry wires, just kinda glitches randomly so I thought it could be the computer


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check the grounds out, maybe a wire is 1/2 falling off the ground loop.

I just went through my whole grounding system. I had replaced all my wiring last summer with 0/1 gauge. The connections seemed solid aside from a slightly loose clamp on my negative. Still tight but I was able to move it. The wires were corroded a bit like so...



Replaced the clamp, the wire above, and cut back the other wires a bit. Also I'm taking off the connections to the block and etc and taking a bit of sandpaper and electrical cleaner to it before putting it back on tight. What do you guys think? Also, can somebody tell my what this small black wire and hoop around the one wire is for?




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Probably a ground.

This could be the culprit. It appears the wires gets too hot from the engine and has melted the insulation into the wire



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Hell yeah.

So now how should I go about redoing this without the whole melting bit? Cut back and insulate differencing for the last couple inches?


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where does that wire go to? what type of end was on there?

best way is to solder a new end on. its real easy if you have a plumbers propane torch, flux and pipe solder.

ive done this method to do thick cables. you dont need those pellets they sell just plumbers solder, and plumbers flux. heat the terminal, and keep filling it with solder till its like 1/2 or a bit more full, then pushe the cable in like shown in the vid. once its cooled off its not coming off.

That's how I do it minus the pellets

That wire that was melting was the ground going to the block right under the front exhaust mani. And I had it clamped in good, the problem was the insulation on the wire itself got hot enough to melt I guess. So this time I made it as low and away from the exhaust as possible. Just gotta find a way to better insulate that wire.

And I got it all done and went for a bit of a drive and so far all seems well again. I'll let you guys know if it happens later on!


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keep a eye on that wire. if need be put some wire loom over it.

Is there a wire loom that would protect it from heat? I'm thinking because it's right at the end where it connects that it gets hot, I might not be able to help things. I cut back the insulation and used a thick wrap of electrical tape since I heard it doesn't melt easily. I could be wrong, but if anything I'm not in any worse doing so. I got it pointed as far away as possible so I guess I'll watch it and see


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Also, what do you guys thinkno that spray you can get to protect the post and stuff from corrosion? Maybe I should spray everything good with that and try to prevent the corrosion that had built up last


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ive never had to use that stuff myself. cant hurt. i also never had my terminals corrode up on any of my cars. i see it all the time on my friends exploder. fords ya know lol

Lol and my car I guess... I wonder if its something to do with my wires not being "automotive grade" :P I always thought they used that really hard crap because it was the cheaper route for them


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On my old car I had corrosion problems on my wires. I remember going to watch my girlfriend's soccer game and when I was going to leave, I had no power. Spent over an hour checking stuff, then looked at the wires connected to the battery and they were getting all funky lol.