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General Discussions about the 300M and other LHs

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 #395948  by Adrian63
 
After I swapped 3 alternators thinking they were bad (flickering lights ,battery warning sign ,random engine turn off and the weird radio whine when accelerating) I arrive to the logical conclusion that the only thing left not checked is the PCM because that's what holds the voltage regulator.

Now the question is can I plug&play swap the PCM /SKIM from my parts car to mine? Mine is march 99 and parts car was january 00 both 3.5 v6. I had no idea the PCM could simply disconnect the power so bad that I had to reinsert the radio code....this happened last night.
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 #395949  by LUNAT1C
 
Did you check the battery? Are the body and engine grounds clean, tight, and in good shape? There are ground straps on both sides of the engine.

I'm not certain, but I believe the BCM is part of the PCM/SKIM mix. At that point, I believe they can be hot-swapped and work with the chip key associated with the replacement SKIM taped to the column.
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 #395951  by Adrian63
 
LUNAT1C wrote: June 14th, 2024, 10:25 am Did you check the battery? Are the body and engine grounds clean, tight, and in good shape? There are ground straps on both sides of the engine.

I'm not certain, but I believe the BCM is part of the PCM/SKIM mix. At that point, I believe they can be hot-swapped and work with the chip key associated with the replacement SKIM taped to the column.

Well the ground is ok. The only thing that was worked on 4 years ago was the positive cable which some electrician made a "marine knot" or something .I change the wire where the fusible link is and like 10 inches above the fusible link the "expert" did a knot and wrapped it in electric tape and I really suck at electrical stuff but I know that can get you high resistance . Could it be that connection oxidized over time and now gets poor connection? I know about the voltage regulator in the PCM but I don't think the voltage regulator could shut down the car in such a way that I need to reinsert the radio code.

I can't believe I change 3 alternators thinking they sure are bad. What tricked me was the whine radio like sound that was getting higher when I was driving and lower at lower rpm.

I have the PCM/SKIM and BCM + key from my 2000 300M parts car and I don't think if I swap them all I need any dealer for reprograming.

The engine ground straps should be above the exhaust manifolds right?
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 #395953  by LUNAT1C
 
Having all those parts, dealer DRB-III shouldn't be necessary. You'll just lose the immobilizer feature.

I've never heard of "knots" in electrical wiring. If that's what I think it sounds like (literal knot, like tying a boat to a deck cleat, or tying shoelaces?) yes that will cause added resistance.

Alternator whine can be cause by a failing alternator, and by bad grounds. Bad grounds are more common. Check the battery ground, check the engine grounds (yes, above manifolds and bolt to the body), and the PDC grounds on the driver side fender. If they're all tight, clean, no broken or frayed cables or straps, check grounds inside the car near the BCM. Bolted to the body.
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 #395955  by Adrian63
 
EDIT: So I fixed it and the problem was not the wire but the AC compressor . For some reason the compressor was cutting the power. I knew it had a whine and I thought it was the clutch but never paid too much attention because it worked. I was going to swap it with the one from my parts car but I postponed it (3 years lol ) because I was thinking I have to refill it.... I had no idea AC compressors can do that to a car.