Under the battery tray

 

Under the battery tray! Thank you!

 

Did you find it? let us know.

I gotta ask WHY are you looking for "PCM" on a your 2007 commander?

 

jtec: I have a 2008 Jeep Grand Cherokee 3.0L CRD, recently the alternator died and I ran the voltage way too low trying to get home. After replacing the alternator the voltage is unreliable. After a few starts no voltage is coming though the system as if the alternator wasn't working. If I disconnect the battery terminal and reconnect (reset the system), voltage is 14.5 V as expected. My understanding is that the voltage is regulated through the PCM and that is likely the issue.

Do you have any insight on this issue or were you just trolling the original poster?
https://www.jeepforum.com/forum/f67/replaced-alternator-but-no-charge-after-starting-twice-4445223/

 

Have you tested your battery after this?

 

FYI: For what ever reason jeep calls the module a ECM on diesels :dunno: acronym overload.

pretty simple circuit for alt - 3 wires the big cherging wire and 2 field wires.

Be sure there is 12v at big wire with eng OFF. this will test fusible link.
This voltage should increase when charging ck at battery.

The field circuit* - jump the 2 wires with a test light it should blink - yes or no?

* this is circuit controlled by ECM - be sure the wires are good, connectors sometimes a problem poor connection.

 

Thank you for the diagram and responses. I believe this Jeep has only 1 field wire and the large charging wire. Battery is good, new and hods the charge. I'm more convinced than ever that the ECM is the culprit. I'll check the connectors and such again, but the spontaneous way that the charge stops seems like a faulty computer. Every time I disconnect and reconnect the battery terminal everything works perfectly, for a few starts, then back to no charge at all.

Does anyone have a lead on where to get the ECM part and programming it? The places I talked to were having a tough time figuring it out with the 3.0 L CRD engine.

 

What are you using to see that it's not charging? OBDII data? DVM on the battery terminals?

The dash indicator is unreliable. My dash indicator frequently shows the drunk red robot, but the OBDII data shows that the voltage is fine.

 

DAMN we have 2 different posters, and 2 different vehicles.... I'm confused enough without more than 1 car per topic.


bettervibes11 you have a GRAND CHEROKEE 2008 MY with a 3.0L CRD.
See attachment