# Voltage always 15.0v



## Johnny B (Jun 4, 2019)

Well I guess it is possible the battery is going bad, and the PCM is commanding a de-sulfating routine. First question, what is the actually battery voltage. I recommend testing it with a multimeter. Since a recently charged battery can read a false high, after turning the car off keep the low beams on for about 30 seconds. Then disconnect the battery, and test. You should be at 12.6 volts or higher. Or you can do it another, less good, way. After running the low beams, pop the hood and let it sit for an hour. Then measure voltage before messing with anything.

My second question is do you have any extra wiring going to your battery, like for an amp or a big 3 kit? Anything that is bypassing the current sensor will mess up the system.

And lastly, but the easiest thing to do.  After you turn the high beams on the system should shortly go to 15.3 to 15.5 volts, if it is locked in at exactly 15.0 I would say you might have a programming issue.


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## Atstehley (Feb 11, 2019)

Johnny B said:


> Well I guess it is possible the battery is going bad, and the PCM is commanding a de-sulfating routine. First question, what is the actually battery voltage. I recommend testing it with a multimeter. Since a recently charged battery can read a false high, after turning the car off keep the low beams on for about 30 seconds. Then disconnect the battery, and test. You should be at 12.6 volts or higher. Or you can do it another, less good, way. After running the low beams, pop the hood and let it sit for an hour. Then measure voltage before messing with anything.
> 
> My second question is do you have any extra wiring going to your battery, like for an amp or a big 3 kit? Anything that is bypassing the current sensor will mess up the system.
> 
> And lastly, but the easiest thing to do.  After you turn the high beams on the system should shortly go to 15.3 to 15.5 volts, if it is locked in at exactly 15.0 I would say you might have a programming issue.


I forgot to attach the results of the test, oops. Voltage was 12.08 after about 4 hours of sitting at 37°F. Not great voltage retention, but it could be worse. I'll check load conditions on my way home tonight. Thanks for the suggestions!


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## -loki- (Dec 13, 2019)

Check your grounds... there is a TSB on this.


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## Atstehley (Feb 11, 2019)

-loki- said:


> Check your grounds... there is a TSB on this.


Is that the negative cable TSB or is there a separate? I do have the original design cable still.


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## Johnny B (Jun 4, 2019)

Atstehley said:


> Voltage was 12.08 after about 4 hours of sitting at 37°F


Well there is your problem ! 

Granted a car battery should last longer than two years, but it seems pretty clear to me it is the problem. The system wants to charge the battery to about 80% but can't get it there.
And your battery report basically says that as well. Because at 15 volts that battery should be fully charged basically all of the time. A having said that, maybe the system is over charging and killing your battery. But I think you will need a new battery to prove it.

When you change the battery clean all the connections with a battery terminal cleaner. Those are the best, and only cost $5. Also, check the negative to chassis mount for corrosion or other damage.
Actually you know what, do this first it might save you from getting another battery.


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## Johnny B (Jun 4, 2019)

Maybe !?!?






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## -loki- (Dec 13, 2019)

Doubt the battery is ruined if it only has happened recently... more than likely a poor connection is bleeding off some of the voltage. Put that battery on a good charge out of the car and it will more than likely be fine.


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## Atstehley (Feb 11, 2019)

-loki- said:


> Doubt the battery is ruined if it only has happened recently... more than likely a poor connection is bleeding off some of the voltage. Put that battery on a good charge out of the car and it will more than likely be fine.


Thanks for the help guys. I'll pull my battery out while I'm at work and throw it on one of our chargers. I'll check the grounds out while I'm in there. I don't have any symptoms of the ground failing (no tsc lights or radio issues, although my speedometer sometimes freaks out?) But I'll look into it. Thanks again!


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## snowwy66 (Nov 5, 2017)

How do you figure out 465 out of 525 amps?

What test is there?


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## Atstehley (Feb 11, 2019)

snowwy66 said:


> How do you figure out 465 out of 525 amps?
> 
> What test is there?


Test was completed using a Megatronix analyzer. 525 is sticker rating in CCA. Analyzer performed a load and voltage test on the battery and gave me the posted results c:


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## Snipesy (Dec 7, 2015)

The BCM has a state of charge PID. Which is what the charging system resolves around.

Its a guess by the BCM adjusted using the current sensor.

However when disconnected we can use charts like this to determine it. Its battery specific you'll have to find the chart for your type of battery. These charts will not work when any current is being drawn.









If the BCM value isnt matching up the predicted disconnected SOC, then its an issue with the current sensor or BCM. Or a strange wiring issue.


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