"Check Battery" voltage high - JeepForum.com
 
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post #1 of 7 Old 07-23-2019, 12:50 AM Thread Starter
FlamingRain
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"Check Battery" voltage high

I was driving home last night, and I got a nice idiot light on the dash and a "check battery" message at the VIC. I looked over and the voltage reading on the dash was at 17+ volts, well into the "red". This only lasted about a minute and a half before dropping back to 14 volts. No other issues (that are related). Starts and shuts down fine, and no behavior changed whatsoever when this happened. Should I be concerned? Is it possible something just shorted out temporarily and caused this? I've never heard of this before and googling only turns up bad PCM which seems to be a more consistent error when the voltage regulator dies.


2wd can really get you places you can't get out of without 4lo. - Ratmonkey
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post #2 of 7 Old 07-27-2019, 01:42 PM
jrcromwell
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The PCM controls the field voltage by increasing or decreasing voltage to the field to increase or decrease alternator output.

If the PCM is trying to lower the output and does not see the output lower it will max the in-dash gauge.

The PCM does the same thing if it is trying to increase alternator output and does not see an increase it will drop the gauge to Zero.

If you were to use a meter and check voltage from ground to alternator output post and then from positive to negative across the battery I would be very surprised if it was actually overcharging. I would check it but keep a meter on hand to check it when it claims to be overcharging.

I would expect to see 13.8-14.5VDC. KOEO (running). I see this generally in the summertime when the PCM attempts to derate the output in response to battery temperature sensor input.

If my charging rate was correct when the message occurred I would not worry about it.

I use a one-wire self-regulated alternator and use an AGM battery I use to get this message in the summer with a lead-acid battery but have not since switching to am AGM battery.
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post #3 of 7 Old 08-04-2019, 07:14 PM
peter_zabriskie
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I just saw this on my 97 ZJ. My battery died and after a jump start I drove to the parts store to buy a new battery. The voltage meter pegged at 19 after driving a mile. I pulled over and put the shift in Park....and it came down to normal 14. I drove off and after a mile peg to 19 again. Repeating this all the way to the part store. Wierd! Hoping it was a dead cell in the battery. When I got to the store the battery was completely dead. The new battery was put in and she runs like a top. No issues. I think indeed a dead cell or cells inside the battery was the issue.

Prayer does not use up artificial energy, doesn't burn up any fossil fuel, doesn't pollute.M.Mead
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post #4 of 7 Old 08-05-2019, 03:10 PM Thread Starter
FlamingRain
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Update. This goes a bit further than just the battery voltage, but I didn't want to start a new thread for something that is probably related.

Last night when driving home my ABS light came on. No symptoms of anything. I stopped at a store, started it again, and the ABS light turned off, but the check engine light came on. Then, the coolant temperature sensor dropped to zero. I had been driving for 20 minutes, so there's no possible way the coolant was stone cold. I went to NAPA earlier today to get the code checked (still no actual symptoms), and it was P0117 coolant temp sensor voltage low. While I was checking, the gauge started pinging between max and stone cold, cycling every 10 seconds or so. Occasionally it reads what is the correct temperature. Should I bother trying to change the sensor (and where is it actually?) or is the PCM likely glitching out or something is shorted?

2wd can really get you places you can't get out of without 4lo. - Ratmonkey
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post #5 of 7 Old 08-06-2019, 11:59 AM
jrcromwell
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If you have not already done it I would clean all chassis and engine grounds first. Clean like shiny clean I also add star washers to ensure a good bite and after reinstalling I hit them with a quick spray of gloss black to seal them.

The PCM could be an issue but all of the instrument cluster coils are driven from the info sent from the PCM via the CCD bus.

The ABS lamp is controlled by the CAB(controller anti-lock brake) directly, so the CCD bus is not involved in that circuit.

Having multiple issues is a possibility ie faulty speed sensor causing an ABS indicator and dirty grounds. The idea here should be to divide and conquer.

Start by cleaning all grounds as described then wait to see if the problems come back or maybe that does nothing for you. If it is the later there could be some corrosion or a poor connection on any of the modules connected to the CCD bus. That includes the factory head unit if you still have it.

The logical place to start would be the connector for the instrument cluster. I would only perform one task at a time that way if you fix it you know exactly what fixed it.

More importantly, if you introduce a problem you know what you last touched so you can quickly go and face to palm because that connector wasn't installed all the way.
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post #6 of 7 Old 08-06-2019, 02:05 PM Thread Starter
FlamingRain
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Thanks for the advice. As is usual on electric gremlins, especially intermittent ones, I had kind of figured cleaning the grounds was in order. I decided to start with what might be the most related, the PCM ground, where also what looks like the alternator grounds out to as well. Knock on wood, the code went away (had the battery disconnected) and the coolant temp sensor is reading accurately now. Will update if any funny business returns.

2wd can really get you places you can't get out of without 4lo. - Ratmonkey
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post #7 of 7 Old 08-07-2019, 11:43 AM Thread Starter
FlamingRain
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Spoke too soon I guess, I got about half way to work before the gauge started losing its mind again. It appeared to have some kind of effect, so Iíll double check the wires themselves for any issues/binding and then Iíll head onto more grounds.

2wd can really get you places you can't get out of without 4lo. - Ratmonkey
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