Hi, I have 99 jeep grand cherokee 4x4 4.7.... my problem is that, I've replaced the pcm (twice), new battery, new alternator (twice as well). I've checked for loose grounds, shorted wires (in the engine bay wiring harness) and have come up short of seeing anything wrong. I had the alternator checked and one shop said it was fine, had another shop check it and they said the alternator was no good. So, I get the replacement alternator, Install, BAM! it's starts charging and running as it should. Take a short drive and then park for about an hour or so, come back and go to drive off and wouldn't you know that the new alternator is not charging just as the previous one had. I'm at a loss here... I know these jeeps have issues but please if anyone can help with this it would be much appreciated!

 

Welcome to the forum.

Have the connections been disassembled, inspected, cleaned, reassembled and properly tightened?

Has the charging system been tested per the FSM?

Has the wiring been inspected, including measuring continuity while flexing.

 

Connections were cleaned before reinstalling. Has anyone had this issue before.

 

The connections at the generator as a small part of the connections that will affect the charging system. All of the power and all of the grounds must be clean and tight.

Also, the generator field wire conductors are "small" and could be degraded by heat and vibration. It is good practice to measure continuity while flexing.

 

There is also a temperature sensor underneath the battery that tells the PCM to cut back the charge rate when the battery gets hot. This may be faulty and not allowing the battery to charge properly. Most people don't even know it's there.

 

I'll replace that and get back. Hopefully it's that

 

Why the shotgun approach to vehicle repair?

Just diagnose the problem and fix only the fault?

The FSM has everything required to ID the root cause.

 

I get no codes for anything other than an o2 sensor. I get no codes for anything else. It's done the whole stalling thing.

 

What is the "fsm"?

 

FSM is Factory Service Manual, like here.

 

Think you. I'll look into it this evening after work. Thanks for the advice I've recieved.

 

is there any one vendor with a latest release/update?

 

try pacificcoastmanuals.com

 

With the scan tool, how many monitors show 'incomplete'? If there's like 4 you may have a problem in the battery temperature sensor.

 

No codes shown/read. Bit the bullet and bought a new battery temperature sensor with fingers crossed and no luck...