Do I need a new PCM?

[lonelytoilet]

Before I go dishing out the clamshells to WranglerFix to check out, or replace, my Power Control Module (PCM), I was wondering if others would be willing to put their two cents in about my Jeeps current calamity. I've got a 2002 4.0L Inline 6. At first, I had the check engine codes p1495 and p1682 and my alternator was only charging to 12 volts, but it was charging. I replaced the alternator and battery and there was no change in how the car was charging. Just prior to taking it into an automotive electrical shop I got the code p0443. The guys at the shop said, unsurprisingly, the PCM was at fault for the charging problem and that all electrical connections and grounds looked good. As a bandaid to the problem, they strapped an external voltage regulator which is maintaining a nominal 14 volts on my system. Overall, I've now got the following codes in simultaneously:

1. p1682 - Charging System Voltage Too Low
   1. "Charging system output voltage low."
2. p1594 - Charging System Voltage Too High
   1. "Battery voltage sense input above target charging voltage during engine operation."
3. p0622 - Generator Field Not Switching Properly
   1. "An open or shorted condition detected in the generator field control circuit."
   2. (expected considering the external voltage regulator is in place of the PCM regulator.)
4. p0443 - Evap Purge Solenoid Circuit
   1. "An open or shorted condition detected in the EVAP purge solenoid control circuit."
5. p1495 - Leak Detection Pump Solenoid Circuit
   1. "An open or shorted condition detected in the Leak Detection Pump (LDP) solenoid circuit."

Thoughts?

 

[Chris]

@Wranglerfix

 

[williambmac]

Alternator voltage is regulated by the PCM, so it very well may be your problem.
The other charging system codes that you now have are due to your shop installing an external voltage regulator and bypassing the PCM.
The PCM is not seeing the correct parameters.
I would want everything back to stock. I would then check all battery cable connections .
I would also want a DMM across the battery terminals to see what the actual running loaded/unloaded voltage reading are.

As for you P1495, that is going to require additional diagnostic. Possible PCM, wiring or an internal fault with the pump itself.

 

[pagrey]

Cables that look perfect can be internally corroded. Before I replaced a PCM I'd very carefully check all the cables, especially every ground you can find.

 

[Wranglerfix]

@lonelytoilet I can test your ECM for you at no charge if you send it into me. If there is something wrong with it the repairs are 100-150. Testing normally takes 2-3 days.

It could be a loose/dirty ground, frayed wires, ecm or a combination of all of the above.

 

[qslim]

Did you ever check wiring per the schematics that we posted in your other thread?

 

[lonelytoilet]

I've checked as much as I can for now, in terms of electrical. Admittedly, I definitely haven't done the greatest job checking, but I haven't got much time to tear into and check all of the wires thoroughly like I'd want to. @Wranglerfix I'm gonna take a guess and send it to the address on your website?

 

[Hockey guy]

So old thread but I’m having the exact same issue on an 01 TJ 4.0. EVAP purge, leak detection, and alrernator not sending. So it SOUNDS like the evap purge, and leak detection pump are related to the regulator. Correct??