The dreaded battery light issue…

[KillerRubi]

Hi all,

I know after reading hundreds of threads that this issue has been covered to death so apologies in advance for another battery light issue thread, however, I’m struggling to find someone having my exact issue and a possible solution.

I’ve owned the car for 3 1/2 years and have done over 30k miles. From the very beginning I’ve had an intermittent battery light issue where the red low battery light will come on seemingly randomly, sometimes it won’t happen for weeks, other times it will be every 5 minutes. Strangely, the actual voltage can read anywhere from 11.7V to 13.4V. In addition to this, it will sometimes display the “Stop Safely, Vehicle Will Shut Off Soon”. In both cases, a quick restart of the vehicle clears both warnings and everything is seemingly normal.

In the majority of the posts I’ve read the above issues eventually lead to some kind of catastrophic failure that leaves the Jeep inoperable. However, in my case, in the 3 1/2 years I’ve never had a catastrophic event, the Jeep has never actually shut off and the batteries have never died, it’s just the warning lights that have persisted. Even stranger, even though the low voltage battery light is on the ESS will often still work.

For reference, it has been in and out of the Jeep Dealership multiple times for diagnosis and despite changing batteries, alternator and main fuse the issue has persisted. After multiple visits in the space of 12 months when each time they claimed it was resolved, they washed their hands of it citing the accessories being fitted to the vehicle was likely causing the issues. At the time I was exhausted having to fight and repeatedly take the Jeep to the dealership over 200 miles away and given it never actually died I gave up trying to get it resolved through Jeep.

So three years on, it’s now out of warranty so the dealership route has sailed and I’m potentially looking to sell the vehicle due to relocating overseas. I would really like to resolve the issue once and for all as I don’t feel comfortable selling the vehicle with the warning lights and to be honest it would be great to finally know the root cause.

I’ve recently engaged a highly recommended auto electrician to help diagnose the issue but he is equally stumped so if anyone has any thoughts they’d be willing to share it would be greatly appreciated

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[58Willys]

Charge and load test battery, if you have the aux battery separate and charge/test each separately. If one is bad, replace both. Check charging system. Check and test cables and grounds.

If your system is reading 13 volts, batteries are probably bad and not taking a charge.

 

[BigGame]

I’m sure the electrician looked at the alternator connections. Almost seems like the alternator stops feeding battery for a bit. Good luck

 

[alphawolff]

Perform a voltage drop test between the engine block and the battery ground. I suspect you have a loose/bad block ground causing the voltage to drop 0.4v or so below the target threshold. The battery light will only sometimes illuminate when it is that small of a gap. It could explain how it's so intermittent. We had a similar issue with a 2.0L right off the truck. Took about 800 miles before we narrowed down the issue. Could drive it 50+ miles and it'd be totally fine, then the customer picks up and it comes on within a mile.

The voltage drop test shouldn't be more than 0.5v at max, but ideally 0.1 or so. You can verify the charging issue by monitoring the target charging voltage and voltage sense data readouts in the PCM. Target should always be within 0.1v of actual.

 

[Flip]

@KillerRubi

After reading hundreds of threads why not take the aux battery out of the equation. Disconnect the negative and pull F-42 fuse.

 

[KillerRubi]

Perform a voltage drop test between the engine block and the battery ground. I suspect you have a loose/bad block ground causing the voltage to drop 0.4v or so below the target threshold. The battery light will only sometimes illuminate when it is that small of a gap. It could explain how it's so intermittent. We had a similar issue with a 2.0L right off the truck. Took about 800 miles before we narrowed down the issue. Could drive it 50+ miles and it'd be totally fine, then the customer picks up and it comes on within a mile.

The voltage drop test shouldn't be more than 0.5v at max, but ideally 0.1 or so. You can verify the charging issue by monitoring the target charging voltage and voltage sense data readouts in the PCM. Target should always be within 0.1v of actual.

Thanks @alphawolff for the quick reply, it definitely seems like it could be a loose ground/connection as that would explain why it’s intermittent, can you explain exactly where it is or provide a photo please?

 

[KillerRubi]

@KillerRubi

After reading hundreds of threads why not take the aux battery out of the equation. Disconnect the negative and pull F-42 fuse.

Thanks @Flip, I’ve already tried isolating the auxiliary battery, ran it that way for several months however the issue was still happening.

 

[alphawolff]

Thanks @alphawolff for the quick reply, it definitely seems like it could be a loose ground/connection as that would explain why it’s intermittent, can you explain exactly where it is or provide a photo please?

Before even jumping down that rabbit hole perform the voltage drop test.

Using a DMM put one lead on a viable engine ground point such as an alternator bolt. Put the second lead on the negative battery terminal. Set the DMM to voltage and have someone crank the engine while monitoring the meter. It should stay near zero volts (mv doesnt count) during the engine crank. If you see it jump over 0.1v that's suspect, but definitely an issue if it's over 0.5v.



Essentially this tests allows to meter to act as an additional engine ground. Because this voltage goes through the meter's high resistance the electricity should prefer the path of less resistance, aka the normal block ground. If you're getting voltage during this test it means the high resistance in the meter is an easier path to ground than the engine ground, meaning the engine ground isn't doing its job.

 

[mmcbeat]

I don’t drive as much as you do, sometimes two or three days without driving. About once a week I put a battery tender on my jeep. I have a low amp Battery Tender brand. Works great for me, I’m on my third Wrangler. I usually trade vehicles before the warranty expires. If I keep my current 2024 past its factory warranty I will probably remove the auxiliary battery. Oh yeah, every time I start the Jeep I hit the S/S button with my pinkie so it’s always off.

 

[KillerRubi]

Thanks @mmcbeat, I’ve actually installed a permanent solar panel on the bonnet so in theory it’s permanently trickle charging, at least when it’s not dark and raining in the UK which tends to be 9 months of the year

Jokes aside, I have a Noco trickle charger that I also use and unfortunately it hasn’t resolved the issues either.

 

[KillerRubi]

Before even jumping down that rabbit hole perform the voltage drop test.

Using a DMM put one lead on a viable engine ground point such as an alternator bolt. Put the second lead on the negative battery terminal. Set the DMM to voltage and have someone crank the engine while monitoring the meter. It should stay near zero volts (mv doesnt count) during the engine crank. If you see it jump over 0.1v that's suspect, but definitely an issue if it's over 0.5v.



Essentially this tests allows to meter to act as an additional engine ground. Because this voltage goes through the meter's high resistance the electricity should prefer the path of less resistance, aka the normal block ground. If you're getting voltage during this test it means the high resistance in the meter is an easier path to ground than the engine ground, meaning the engine ground isn't doing its job.

Thanks, I’m going to be trying this today and will keep you posted

 

[JLJeepGuy513]

Hi all,

I know after reading hundreds of threads that this issue has been covered to death so apologies in advance for another battery light issue thread, however, I’m struggling to find someone having my exact issue and a possible solution.

I’ve owned the car for 3 1/2 years and have done over 30k miles. From the very beginning I’ve had an intermittent battery light issue where the red low battery light will come on seemingly randomly, sometimes it won’t happen for weeks, other times it will be every 5 minutes. Strangely, the actual voltage can read anywhere from 11.7V to 13.4V. In addition to this, it will sometimes display the “Stop Safely, Vehicle Will Shut Off Soon”. In both cases, a quick restart of the vehicle clears both warnings and everything is seemingly normal.

In the majority of the posts I’ve read the above issues eventually lead to some kind of catastrophic failure that leaves the Jeep inoperable. However, in my case, in the 3 1/2 years I’ve never had a catastrophic event, the Jeep has never actually shut off and the batteries have never died, it’s just the warning lights that have persisted. Even stranger, even though the low voltage battery light is on the ESS will often still work.

For reference, it has been in and out of the Jeep Dealership multiple times for diagnosis and despite changing batteries, alternator and main fuse the issue has persisted. After multiple visits in the space of 12 months when each time they claimed it was resolved, they washed their hands of it citing the accessories being fitted to the vehicle was likely causing the issues. At the time I was exhausted having to fight and repeatedly take the Jeep to the dealership over 200 miles away and given it never actually died I gave up trying to get it resolved through Jeep.

So three years on, it’s now out of warranty so the dealership route has sailed and I’m potentially looking to sell the vehicle due to relocating overseas. I would really like to resolve the issue once and for all as I don’t feel comfortable selling the vehicle with the warning lights and to be honest it would be great to finally know the root cause.

I’ve recently engaged a highly recommended auto electrician to help diagnose the issue but he is equally stumped so if anyone has any thoughts they’d be willing to share it would be greatly appreciated

Ive been experiencing the exact issue as well. i've also been through most steps ive read and still stumped. The jeep can go days with no warning but will randomly have low voltage sitting around 11.7v. I have also noticed that the engine seems lower on power when this occurs. I'm thinking another possible issue could be the PCM but i have no idea on how to go about testing it.

 

[KillerRubi]

Before even jumping down that rabbit hole perform the voltage drop test.

Using a DMM put one lead on a viable engine ground point such as an alternator bolt. Put the second lead on the negative battery terminal. Set the DMM to voltage and have someone crank the engine while monitoring the meter. It should stay near zero volts (mv doesnt count) during the engine crank. If you see it jump over 0.1v that's suspect, but definitely an issue if it's over 0.5v.



Essentially this tests allows to meter to act as an additional engine ground. Because this voltage goes through the meter's high resistance the electricity should prefer the path of less resistance, aka the normal block ground. If you're getting voltage during this test it means the high resistance in the meter is an easier path to ground than the engine ground, meaning the engine ground isn't doing its job.

Finally did the test and exactly as you predicted it read 0.9v so then went and checked the earth underneath the left hand guard and it was actually sparking every time the car started.

Removed the earth, cleaned the endpoints and reattached, no sparks on start up and now the voltage reading in the car is consistently reading 14v at idle whereas before it was reading 13.2-13.4.

Thanks so much for the guidance @alphawolff, hopefully this is the end of an almost 4 year saga

 

[alphawolff]

Glad to have helped!

 

[KillerRubi]

Ive been experiencing the exact issue as well. i've also been through most steps ive read and still stumped. The jeep can go days with no warning but will randomly have low voltage sitting around 11.7v. I have also noticed that the engine seems lower on power when this occurs. I'm thinking another possible issue could be the PCM but i have no idea on how to go about testing it.

Definitely worth checking the grounds under the front wheel arch, the low voltage could be a sign of resistance somewhere. Out of interest, what is the highest voltage you see, mine never went above 13.4 and now it’s sitting on 14 at idle?

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