Random battery light and low voltage

[cram501]

This is a 2019 Wrangler MOAB.

About 6 weeks ago, I got the battery light and the other various lights when voltage gets low (electrical, abs, radio turned off, no power steering, etc..). I restarted the Jeep a few times and the issue disappeared. When I checked the battery voltage, it was low at 12.1 volts. I recharged the batteries with my Noco charger and everything seemed fine. I'm retired so I don't drive as many miles as I used to do.

Every few days I get a low voltage error and the EVIC shows a low voltage of between 11.6-11.9 volts. The battery voltage appears fine. It only happens when the Jeep is started and doesn't occur once it's started and working fine.

I put in two new batteries and a new IBS. I assumed I had damaged the batteries with the initial low voltage problem. The low voltage errors are still randomly occurring. It's still under warranty for another 6 months so I can take it in but I've been unable to replicate it.

Does anyone have any idea on next steps before I take into a dealership?

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[58Willys]

Check all battery cables and grounds. Did you reprogram the IBS? What does your voltage meter read with engine running? If your not getting at least 12.8 volts, the have your charging system checked.

 

[cram501]

The battery cables are good. I've looked at the grounds (passenger side, passenger side wheel well, and engine ground up in the middle - this one I need to take a closer look at since it's hard to get at).

The IBS will be on it's third start after 8 hours today (if that is what you mean by reprogramming the IBS).

Under normal circumstances, the voltage in the EVIC looks good ~13v and greater. When the problem occurs the voltage is in the upper 11's (11.6-11.9 volts).

 

[58Willys]

Try keeping on the charger if you don’t drive everyday, see if that solves the problem.

 

[garyji]

If your batteries are good, there is no reason to put them on a charger for just a few days sitting.

IF the batteries are in fact, OK, then what Geoff said.

G.

 

[cram501]

I fully charged the batteries before the installation. I'm driving enough right now a charger isn't necessary. When life settles down and I'm not driving as often, I'll put the Noco on regularly.

I've only had the issue happen once since installing the new battery and ibs. This was a few hours after installation. Tomorrow should be the 4th time for the IBS (8 hours before start), so I'll just have to wait and see if the error occurs again.

 

[alphawolff]

This is a 2019 Wrangler MOAB.

About 6 weeks ago, I got the battery light and the other various lights when voltage gets low (electrical, abs, radio turned off, no power steering, etc..). I restarted the Jeep a few times and the issue disappeared. When I checked the battery voltage, it was low at 12.1 volts. I recharged the batteries with my Noco charger and everything seemed fine. I'm retired so I don't drive as many miles as I used to do.

Every few days I get a low voltage error and the EVIC shows a low voltage of between 11.6-11.9 volts. The battery voltage appears fine. It only happens when the Jeep is started and doesn't occur once it's started and working fine.

I put in two new batteries and a new IBS. I assumed I had damaged the batteries with the initial low voltage problem. The low voltage errors are still randomly occurring. It's still under warranty for another 6 months so I can take it in but I've been unable to replicate it.

Does anyone have any idea on next steps before I take into a dealership?

Battery light indicates a charging issue. It ONLY indicates a charging issue.

Verify target charging, duty cycle, and voltage sense under PCM data. If it's undercharging verify block ground (voltage drop test on crank) and continuity from power cable from alternator (Z-case fuse array). If all OK replace alternator.

 

[cram501]

Battery light indicates a charging issue. It ONLY indicates a charging issue.

Verify target charging, duty cycle, and voltage sense under PCM data. If it's undercharging verify block ground (voltage drop test on crank) and continuity from power cable from alternator (Z-case fuse array). If all OK replace alternator.

Thanks for the clarification on the meaning of the light. The battery is getting charged. I'll need to figure out how to test the voltage drop and continuity but learning is the fun part.

Could you clarify what you mean by duty cycle?

 

[alphawolff]

Thanks for the clarification on the meaning of the light. The battery is getting charged. I'll need to figure out how to test the voltage drop and continuity but learning is the fun part.

Could you clarify what you mean by duty cycle?

The PCM has three relevant data readouts for the alternator.

Voltage sense: What the PCM is seeing as the B+ voltage it's being supplied.
Target charging voltage: What the PCM is desiring for charging voltage. The ranges anywhere from 12.6 to 14.7 under normal conditions.
Generator Duty Cycle: A % from 1-100 to command how much power the alternator should output.

Free tip: If you ever have a battery light on and the duty cycle indicates "8000%" your alternator has both failed AND fried the voltage regulator in the PCM.

 

[d k]

I know this is an old thread…

Where would you see the duty cycle readout of 8000%?

The PCM has three relevant data readouts for the alternator.

Voltage sense: What the PCM is seeing as the B+ voltage it's being supplied.
Target charging voltage: What the PCM is desiring for charging voltage. The ranges anywhere from 12.6 to 14.7 under normal conditions.
Generator Duty Cycle: A % from 1-100 to command how much power the alternator should output.

Free tip: If you ever have a battery light on and the duty cycle indicates "8000%" your alternator has both failed AND fried the voltage regulator in the PCM.

 

[THAW]

I know this is an old thread…

Where would you see the duty cycle readout of 8000%?

In an OBD-II diagnostic tool.

The most convenient one for Jeep owners is JScan, where it'll be in MODULES -> Powertrain Control -> LIVE DATA -> Generator Duty Cycle (%DC).

 

[d k]

thank you

In an OBD-II diagnostic tool.

The most convenient one for Jeep owners is JScan, where it'll be in MODULES -> Powertrain Control -> LIVE DATA -> Generator Duty Cycle (%DC).

 

[alphawolff]

I know this is an old thread…

Where would you see the duty cycle readout of 8000%?

PCM Data. Need a scan tool. Wi-Tech has it labeled as "generator duty cycle"

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