I started the jeep up and it is running real bad missing. I checked the voltage output and it is at 16+ volts, I understand that the voltage regulator is in the PCM not in the alternator also the battery gauge stopped working and it reads check gauges no engine light is on. I used it last week at it ran good. I am thinking that the PCM went bad?
2000 4.0 Grand Cherokee
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It's been raining a lot lately in NY hasn't it? Wet plus corrosion = bad running... agree with JeepWJ19.
Yep! These Jeeps will get really wonky with a bad battery connection, they will also start to freak out when the battery is starting to get weak, before you even notice anything in starting.
Older Chryslers are definitely known for PCM issues but I wouldn't push the panic button on that just yet.
Older Chryslers are definitely known for PCM issues but I wouldn't push the panic button on that just yet.
Clean the battery connections first.
Might need one of those big, heavy aftermarket battery clamps, like the guys who run big car audio. I put one with lots of De-Ox on my '98 XJ positive cable, it had the opposite problem, wouldn't charge at all. Fixed it (3 years ago)! Mine came from Auto Zone.
Ok so I cleaned the battery cables real good, the cable ends are stripped very clean copper all the way around and they are tight, I am pretty sure that the PCM is bad it will go to start then die. Ordered one for $200.00 and it is programmed to jeep !
PCM's of this era are problematic for Chrysler, including the failing regulators for the Alternators which are in the PCM. That said double check everything before condemning the PCM. I would trip the alternator field wires manually and see if you get proper charging voltage. If that checks out then condemn the PCM. Also are you sure the battery is good? (Stress test)
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Be very cautious of your alternator.
I've got a '98 Grand Cherokee that had the "check gauges" warning light. This was with a new replacement alternator. You'd start it up, volt gauge would show good....for about 10 seconds and then it would drop to zero. However, the alternator was charging the battery and it was driven like this for about a month. Hundreds of miles were put on it and the alternator kept the battery charged. Charging system was checked weekly and it was rated at full amps.
The alternator failed and all problems disappeared when a replacement was installed. No wiring faults or bad grounds, it was a defective new alternator that had been replaced a couple of months previous.
I've got a '98 Grand Cherokee that had the "check gauges" warning light. This was with a new replacement alternator. You'd start it up, volt gauge would show good....for about 10 seconds and then it would drop to zero. However, the alternator was charging the battery and it was driven like this for about a month. Hundreds of miles were put on it and the alternator kept the battery charged. Charging system was checked weekly and it was rated at full amps.
The alternator failed and all problems disappeared when a replacement was installed. No wiring faults or bad grounds, it was a defective new alternator that had been replaced a couple of months previous.
Originally Posted By: jeep58
Battery not old 6 months maybe for the cca but its not a small battery, Trip alternator field wires?
Battery not old 6 months maybe for the cca but its not a small battery, Trip alternator field wires?
When mine did that the battery had a bad cell. Those "gauges" on the dash are pretty useless. 9 volts pegged usually means an alternator problem, and 16 pegged means the battery isn't taking a charge.
I'd replace the battery and make sure the connections are clean and tight. FWIW, when this happened to me my battery was 6 months old and just "went bad" randomly. Never had an issue since.
I'd replace the battery and make sure the connections are clean and tight. FWIW, when this happened to me my battery was 6 months old and just "went bad" randomly. Never had an issue since.
I checked the battery it is at 12.6 volts, I went to start the jeep it starts then dies can't get it to idle or run without giving it gas even then it is running real bad missing so I am thinking that the computer is wasted I am thing that the computer will also control the engine running. Again I just used the jeep last week to get inspection done it ran good ( always did have a bit of a funky idle) so maybe computer has been going bad?
I had an internal short in the battery on my Cherokee with these exact symptoms. It would start and run but the battery gauge would peg out and the voltage was low when off.
Nick1994
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Go rent a fuel pressure gauge at the auto parts store and screw it onto the fuel rail and check the fuel pressure. I think it's supposed to be 49 psi? At least on my XJ it is
Have a scan tool? Any codes?
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