Ontario

Hi,

I need some help. I have a 2002 Jeep Grand Cherokee. I had a problem a couple days ago. I was driving home from work when my truck died infront of my house on the driveway.

- I thought it was just a battery problem, so I got a jump from my neighbour, that didn't work, it died minutes later again.

- I took the battery back, replaced it with a brand new one, still didn't work, the batter drained and didn't recharge.

- I changed the alternator with a brand new alternator, still didn't work.

- I also changed the two battery terminal clams with brand new ones, still didn't work.

- I took the truck to a shop today, tested it, all maxi fuses are good, they couldn't figure out what the problem is.

- Now after $250 and after installing a brand new alternator, a brand new battery, and two brand new terminal clamps installed but:

- It still won't charge, the gage keeps going down till it dies, before that all lights on dashboard go on until everything dies out and stalls when the battery is drained.

Does anyone know? Please share your information, I would really appreciate it, please and thank you!!!!!

Hymie

I’m surprised that a garage cannot diagnose the problem. I believe that the charging control is performed by the ECU (and not the alternator). Before spending another $250, take it to a Jeep specialist to get it sorted. Unfortunately, although charge control is only a small part of the ECU’s function – a replacement is not cheap.

tiwvr1

Agreed with above poster.

Hymie

Before spending further money on a replacement ecu, it would be worth taking a look at the electrical connections to the ecu – look carefully for any broken wires, or more likely - carbon deposit on the pins causing a poor electrical connection.

It wouldn’t hurt to give the connecting pins a spray with WD40 or some such proprietary switch cleaner.

Use a multimeter to measure the battery voltage with the engine running, which should read around 14V dc. With no charging, the battery voltage will be around 12V dc or less.

rdaharry

Ok i already replaced the ecu about 6 months ago and now the voltage is low about 12v at idle and nothing on......replaced the alt and no change in the volts, so what else could it be.............

CarolinaZJ

your voltage regulator is bad. get a new one

tiwvr1

voltage reg is in computer. What kind of pcm did u replace it with, a rebuilt one?

Get a multimeter and check for voltage right out of the positive of the alternator, that will rule out wiring from alt to bat. Running should be 14.5 or so. There may be a fusable link between alt and bat. Not sure about jeeps, but some other cars have them.

rdaharry

installed a new pcm/ecm, I will check all the wiring in the morning before work...........

shawnalee

I am having the same problems and was wondering if you ever figured out the problem

Zach Putnam

I have an 02 Jeep Grand Cherokee limited 4.7l that won’t charge at all while running. I have replaced the alternator, battery, battery wire clamps, I have checked the fuses, I replace the connector from my wiring harness to my alternator, I have checked the grounds and raced wires for any break. I am stumped and extremely frustrated on what to do. If I charge the battery myself it will start and run no problem but it will just continue to drain while running, the battery doesn’t drain at all when off. And while running it won’t go over 12v, depending on if I have a load on it like my lights decides how fast it will drain and then die. All dash lights come on before it dies. I checked fuseable link it’s fine. If anybody has any suggestions I would greatly appreciate it. Thanks.

BlueRidgeMark

Here's a suggestion: start a new thread instead of digging one up from 8 years ago.

Noah911

Wires... At the starter and alternator to the battery, and the ground.

There is either bad voltage drop or too much ground resistance in the wires or at the connections on the starter, alternator, or the battery.

The alternator is unable to supply full charging power to where it needs to.. your battery.