Chrysler Pacifica Luxury meets versatility in this mid-sized sport utility vehicle

Low Voltage - Alternator Problems

Old 01-13-2019, 07:01 PM
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Default Low Voltage - Alternator Problems

Okay... had a battery light on. Had symptoms leading to alternator replacement. Still have the symptoms. Let me give you the rundown, and please let me know if I have missed anything.

Replaced the alternator, still low voltage.
Have continuity between the alternator post and the positive battery post.
Have continuity between the brown/black wire and the negative battery post.
Found one wire in the harness leading to the C2 connector for the PCM that was severely damaged. Soldered, shrink tubed.
New alternator tested good by parts store.
Using a bluetooth OBD reader to get voltage from the ECU, as well as a Digital Volt meter to pull the reading from the battery.
Whatever the battery voltage is when the car is off, it is generally .2v lower when running.
When I turn on electrical accessories, the voltage drops lower.
The car will eventually stall if you let the battery go completely flat.

What have I missed? There has to be something I'm overlooking or that I haven't checked yet. I know I need to look at the brown/grey wire from the alternator plug back to Pin 19 on C2 at the PCM. What else could it be? Is it possible that the control circuits in the PCM are bad? What else do I test before coming to that conclusion?

Thanks a ton. This is my daughter's car, and she wants it back. I put her in my beat up old Lexus SC400 until we get this fixed.
Old 01-13-2019, 07:02 PM
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Forgot to mention... 04 Pacifica AWD. 3.5L.

Thanks again.
Old 01-13-2019, 08:45 PM
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Join Date: Aug 2010
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Sounds like you did a pretty through check of the charge system. I was not aware that Chrysler placed the Electronic Voltage Regulator (EVR) within the PCM. A pretty daunting and crazy expensive way to R&R a failed voltage regulator, if in fact that is what the root issue is. Attached please find the factory manual for a 2005 Pac, Generator section and wiring diagram, which will work fine with your 2004. Please double check all and let us know how it goes.

PS - Should the voltage regulator be in fact dead, I would consider wiring up a "new" external regulator rather than fight a PCM replacement.

PSS - I included the battery section for completeness, prolly not needed, the Generator section follows. In true Chrysler tech form, their shop manual does an OK job explaining how the charge circuit is designed to function, but a terrible job of actually troubleshooting it..

PSSS - The external regulator you want is PN ERCKFRM, . If you have any questions call them up direct, 616-785-7990. $65
Attached Files
File Type: pdf
Pac_ChargSyn.pdf (723.4 KB, 14 views)
File Type: pdf
Pac_ChargSyn_Wire.pdf (214.9 KB, 10 views)

Last edited by djetelina; 01-14-2019 at 09:36 AM.
Old 02-27-2019, 04:13 PM
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Just in case anyone reads this... Replaced the PCM. Everything is good now.

Thanks a ton for the external voltage regulator idea. I seriously considered it. Vehicle wiring is not my forte, but it looks like it would have been doable.
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