PCM Capacitors: Replace on 96+ or only older ECMs? - JeepForum.com
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post #1 of 10 Old 02-16-2020, 12:32 AM Thread Starter
StellaTheZJ
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PCM Capacitors: Replace on 96+ or only older ECMs?

I've been trying to track down a condition where the brand new NTK O2 sensor on my 1996, 4.0l ZJ has a strange, lazy-looking graph on a scanner. I've been going through a lot to test it, and I'm starting to wonder if maybe the PCM might have electrolytic capacitors in it that are leaking, like the earlier ZJ ECMs sometimes have.

I found one resource that says no, 96+ PCMs do not have electrolytic capacitors in them, but I also found an eBay site selling caps that supposedly fit 1993-1998 ZJs. I find it hard to beleive that the same capacitor kit would fit the OBDI ECMs and the OBDII PCMs too, but you never know...

Can anyone tell me if the 96+ PCM is indeed free of electrolytic capacitors? Thanks!

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post #2 of 10 Old 02-16-2020, 11:19 AM
MaintMech
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Somewhere in this section there's a write up on "Lazy Caps In PCM" or similar title. It was pretty in depth and should have the info you're looking for.

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post #3 of 10 Old 02-16-2020, 07:00 PM Thread Starter
StellaTheZJ
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Thanks for that, I have seen those threads but they all seem to apply to the 93-95 ECMs. I just wanted to confirm that there wasn't a repair process for the 96-98 PCMs. It turns out there is, it's a matter or resoldering some joints on the voltage regulator header, but I was wondering if there might ALSO be some capacitors that go bad. All my research so far suggests that the 96-98 PCMs do not use electrolytic capacitors, so they can't leak or dry out. That doesn't help me solve the problem I'm seeing, but it helps me move on to looking for some other reason than PCM caps!

Cheers!
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post #4 of 10 Old 02-20-2020, 01:47 PM
mikem350
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Not sure about electrolytic caps, BUT. I ran across a Youtube video showing Grand Cherokee PCM fix. Most fixes only show the big connectors being re-soldered!


It also mentioned re-soldering other PCB pins that mate up with the board that the big connectors mount to. COLD SOLDER JOINTS. Another cause of intermittent stalls, etc. The vid shows details, but I would use non corrosive RTV for electronics instead of reusing the old stuff.


While in there look for swollen leaky caps use 105 degree C hi temp rated if any there

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Last edited by mikem350; 02-20-2020 at 01:53 PM. Reason: added Youtube link
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post #5 of 10 Old 09-29-2020, 10:35 AM
Benthal8
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Quote:
Originally Posted by StellaTheZJ View Post
I just wanted to confirm that there wasn't a repair process for the 96-98 PCMs. It turns out there is, it's a matter or resoldering some joints on the voltage regulator header, ...
Hey, I saw your comment and was wondering where you found the info on reflowing those solder joints in the PCM? (I have a '98 5.9), I've been looking around and haven't seen any info on that or how to identify the voltage regulator and it's pins in there. Thanks!
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post #6 of 10 Old 09-30-2020, 09:04 AM
mikem350
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It is on Youtube. Click the red arrow in the pic.

If that does not work search Youtube for Grand Cherokee PCM fix
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post #7 of 10 Old 10-01-2020, 04:51 AM
Benthal8
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Quote:
Originally Posted by mikem350 View Post
It is on Youtube. Click the red arrow in the pic.

If that does not work search Youtube for Grand Cherokee PCM fix

Thanks, Iíve seen this video before. Kind of cringe-worthy for me when he uses the wire brush on the PC board, and also the way he puts it back together. Yikes! Haha
Anyway I was looking for info specifically about the voltage regular header. But it seems to be right under the plate thatís below the connectors. Not even inside the main box. Glad you sent me back to YT because the last time I looked at these, I wasnít thinking about the voltage regular. Cheers

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post #8 of 10 Old 10-12-2020, 10:10 AM
JeepRocket
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My 97 GC does not use that your of circuit board. It is a flexible type and probably can't be fixed. And yes it has electrolytic capacitors. The area around them is black. Bummer for me!
Look for the taco style pcm casing instead of what u see in that video.
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post #9 of 10 Old 10-12-2020, 10:33 AM
jtec
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Are you SURE there is a PCM issue?
IIRC There is a code for switching slow response, are you seeing P0133?

As the PCM is not *****ing could you describe the issue. Maybe post the graph of voltage yur concerned with.

SORRY I hate the all to easy blame the PCM and condemn them.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #10 of 10 Old 10-12-2020, 07:33 PM
JeepRocket
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Let me clarify what I wrote up there. The one with the flexible PCB and electrolytic capacitors comes in the taco style of computer case. The one with the lid type like you see in those videos if not have the flexible PCB in it. For all I know it could have electrolytic capacitors but I wouldn't know.
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