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brownjeff, ASE Certified Technician
Category: Jeep
Satisfied Customers: 13886
Experience:  17 years experience, ASE certified, dealership certified, Service Manager for 15 years,
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1998 jeep grand cherokee: the pcm..voltage regulator..terminals

Customer Question

1998 jeep grand cherokee larado 4.0 alt. is good is running off the battery no charge is the voltage regulated by the pcm and where is that located does it have a internal or external voltage regulator ive replaced the fuseable link and am ready to run to check for shorts on the wires coming off the terminals next but noone seems to know this .
Submitted: 6 years ago.
Category: Jeep
Expert:  brownjeff replied 6 years ago.
Hello and Welcome to JustAnswer,

My name is XXXXX XXXXX I am here to try and assist your with your question. The voltage regulator for the alternator is internal to the powertrain control module (PCM) and the PCM is located on the passenger's side under the hood on the fire wall

Customer: replied 6 years ago.
is the pcm the problem? or is it something else the computer is only one year old
Expert:  brownjeff replied 6 years ago.
Can you tell me with the engine running the voltage reading of each wire on the alternator?
Customer: replied 6 years ago.
no ivegot the alt out rite now but the woman said it stalled on her and when i got it the battery was dead it was charged and driven the gage was at 12 amps and then went to nothing o output
Expert:  brownjeff replied 6 years ago.
Then you do have a charging system problem. I can't say for sure what the problem is with out knowing voltage readings. With the battery being charged and the alternator testing good most likely the PCM has failed but can't say for sure with out doing voltage tests
Customer: replied 6 years ago.
what is the procedure for that reassemble it and check for voltage at the fusebox by the hot and the two green wires coming off the posts on the alt and how do u get to them with the engine running i have a amp tester and it was reading 12 the batteryconect type, but it dropped to o while it was running and hasent come back so i started to check, the alt is verified good and the fuseable link has been replaced the pcm is 300 bucks and not returnable so i kindaneed a definate plan to determine what it is
Expert:  brownjeff replied 6 years ago.
If you can't get to the wires with it running check the wires with an ohm meter to make sure there are no bad wires. Here is a diagram to help

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Customer: replied 6 years ago.
that helps thanks
Expert:  brownjeff replied 6 years ago.
No worries.....

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