What keeps killing my pcm causing my Jeep to not start
05-30-2019, 05:49 AM
#31
CF Veteran
It is a good possibility, as it will ground the driver in the pcm. Good chance that the pcms aren't even bad. This falls under my 'slap in the face' rule. You can't try to fix one thing when another is slapping you in the face; you have to fix that first and see.
05-30-2019, 06:23 AM
#32
CF Veteran
However, concur that PCM may not be fried (although still want to take it apart. Love to take things apart).
05-30-2019, 08:08 AM
#33
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Join Date: May 2012
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Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
I'm going with probably not, as well, but FIX KNOWN PROBLEMS FIRST. You know you have a problem with your O2 sensor. Fix that before you even think about your PCM.
Once you have that fixed, see where you are. THEN if there seems to be another problem, you tackle that problem. Don't try to get them all figured out in your head before you fix what you know is a problem.
I doubt there's any benefit to that. If it is fried, it likely is just a toasted transistor on a chip, which won't be visible without an electron microscope. Obvious burning isn't likely.
05-30-2019, 10:07 AM
#34
CF Veteran
05-30-2019, 04:40 PM
#35
CF Veteran
Anyway, IMO this is the best advice. They may only be asleep and need to be "awakened":
05-30-2019, 04:47 PM
#36
Newbie
Thread Starter
Okay so i got a new pcm cause the last one i got had a warranty and i put it in and a new 02 sensor and it’s running now. And I’ve plugged the other pcms in and they don’t work
05-30-2019, 05:04 PM
#37
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05-30-2019, 06:00 PM
#38
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Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
Yes, probably the most common failure point, but usually from drying out. They are electrolytics, and unless they have ruptured, they look fine. This kind of failure will much more likely be a driver transistor on a microchip. Possibly a power transistor on the board, but again, visible damage isn't likely. It would be very hard to see, too, as it's hidden under the potting compound. That stuff is thick and deep on those things, and you can't see the board clearly under it`. For any such damage to be visible, it would have to be so bad that it burns through the main board, which is not likely at all.
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