2002 Wrangler - Battery Overcharging P0622, P1594 - Jeep Wrangler Forum

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Old 02-07-2011, 12:13 PM
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2002 Wrangler - Battery Overcharging P0622, P1594

I have a 2002 Wrangler with only about 50k miles on it. Recently I got the check gauges light, and shortly after that I lost all electric while driving. I drove straight into the neighborhood garage and got the alternator replaced, but the mechanic said I'd also have to replace the ECM/PCM. He couldn't get an OEM anywhere, so I drove home with it and I got the check gauges light again. I noticed the volt meter was up around 17 or 18, running pretty high. After that I smelled the dreaded rotten eggs from the battery overheating and steaming up. I got it home and checked the codes, when I found:

P0622 - Generator Field Not Switching Properly
P1594 - Charging System Voltage Too High

I called the mechanic back and he said yes, he was seeing the same codes. He said the voltage regulation is in the ECM/PCM, and that it is fried. It's telling the alternator to run 100% of the time to charge the battery. That's why my alternator died, but if I keep driving around I'll just burn-out the new alternator as well.

I go out and buy a rebuilt PCM from a site recommended by some posters on various Jeep boards. Got that installed yesterday. Start it up and the check gauges light still coming on, volts still running high, battery still overcharging and steaming. Still getting the same two codes.

At this point I'm about $600 in the hole and still nothing fixed. Any help would be so appreciated you don't even know.
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Old 02-07-2011, 09:47 PM   #2
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i have seen this when the cables to the batt are going bad.start by cleaning the connections

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Old 02-07-2011, 10:23 PM   #3
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I think I remember reading this problem can also be caused by a faulty temp sensor that sits underneath the battery...but I could be mistaken...
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Old 02-08-2011, 07:57 AM
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Thanks for these replies. I have already cleaned the connections but I'll check the cables as well. Could be some corrosion from the battery overheating I would imagine. I've checked the sensor under the battery, but other than checking for voltage in the circuit not sure if there's anything else I can look for?
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