Jeeps2Little
Well-Known Member
- First Name
- Chris
- Joined
- Feb 6, 2022
- Threads
- 12
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- 219
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- 451
- Location
- Lost in Utah
- Vehicle(s)
- 2021 Wrangler Sport S Unlimited 8spd
- Thread starter
- #1
Lots of words, I know. Highlights are in bold for those that can't be bothered to read all the details.
2021 JLU Sport 2.0T Auto, purchased almost exactly 2 years ago, 22,000 miles without issue. Mopar lift installed by dealer since new, running 35's. We do a fair amount offroad including Moab last weekend(Chicken Corners, Potash, Fins and Things, 3D trail all slow and steady jeeping, not being hard on anything). Just had a dealer oil change 70 miles before this story begins.
We are on a long weekend trip about 300 miles from home in SW Utah. Yesterday afternoon we were out on short, mild, out and back 4x4 trail. Trail was rough enough to disconnect the sway bar and air down a bit but the climbs and descents on the way out were all fine in 2wd. Got to the viewpoint at the top, stopped to take a couple photos and look around. 15 min later we climbed back in and started the Jeep, put it in reverse and moved back about 10 feet on flat ground and the battery light came on in the cluster and dinged. Finished reversing and put the Jeep in Park and shut it off. It restarted without issue and battery light was off, alternator voltage was the normal 13.7-14.0ish. Headed back on the trail and on a steeper downhill section I slowed and went into 4Low so I didn't have to ride the brakes as much but it wasn't steep by any means. I had climbed it all in 2wd. I used Manual shift mode to keep it in first as we descended. As we continued the short downhill section the battery light comes on again, off, back on, repeatedly, at various intervals from a few seconds to over a minute with no discernable, repeatable cause. At this point I'm figuring we have the dreaded dead aux battery syndrome as the Jeep is ~2 1/2 years old from build date or maybe we have a loose fuse or battery terminal. We stop at the next convenient flat spot, shut down again, open the hood and pushed on all the fuses and relays, checked the main battery terminals, ground lugs, etc and nothing was loose or obviously wrong. Starts fine again and on back down the trail we go with no warning lights. Again in the steeper downhill sections I put it back 4L and the battery light comes on and off repeatedly, but it never happens on any of the short climbs, just the descents. On a longer (~400 yd) final descent it happened again several times and this time the check engine light comes on too. We stopped at the end to air up(engine running for that) and lock the sway bar back in and it started up again just fine, but still had the check engine light but no battery light. Got on the highway for the short 6-8 miles back to town, watching all the temps and voltage, and everything ran fine.
Long story longer, took it to a dealer this morning thinking it was for sure going to be the aux battery failing. They said they now have to do a 4-5 hour diagnostic test with a special tool that connects with Jeep Engineers. (Apparently Jeep was sick of dealers just replacing batteries left and right and that not actually being the issue.) After the test was complete they had found nothing wrong and the fault code was reset. Fault code was loss of communications to some part of the cooling system. We immediately headed back out to the scene of the crime to see if it was really fixed since it was only a few miles from the dealer. Didn't bother to air down this time but disconnected the sway bar and did the first 400yd climb in 4Low without issue or any warning lights. Turned around and came back down in 4Low as we had yesterday and sure as shit the battery light came back on and off several times. No check engine light this time though and the battery light never stayed on very long. Back to the dealer we go and I make them do the battery tests on both batteries with me watching, as they didn't have a record showing that they had actually tested them earlier in the day. Both batteries tested fine.
It hasn't happened on any flat roads, dirt or asphalt, 4Low, or otherwise. Where would I start looking for a likely culprit? I can't think of anything related to the transfer case actuator lever that would be anywhere near a battery lead or a wire with any significant load. The main battery is tight in the tray, not sure about the aux battery but don't hear any rattling in the front right while driving. Only electrical add on I have is a winch which has been on for almost the whole time and have wrapped those leads and checked them recently for any wear and there was none, and a short there would be a massive failure, not intermittent (yes I know I need to put a disconnect on it by the battery).
Open to any suggestions or productive thoughts on this. Still under factory warranty and the Jeep isn't a daily driver so I am tempted to just let my local dealer at home dig into it but not sure they would even bother to actually figure it out.
2021 JLU Sport 2.0T Auto, purchased almost exactly 2 years ago, 22,000 miles without issue. Mopar lift installed by dealer since new, running 35's. We do a fair amount offroad including Moab last weekend(Chicken Corners, Potash, Fins and Things, 3D trail all slow and steady jeeping, not being hard on anything). Just had a dealer oil change 70 miles before this story begins.
We are on a long weekend trip about 300 miles from home in SW Utah. Yesterday afternoon we were out on short, mild, out and back 4x4 trail. Trail was rough enough to disconnect the sway bar and air down a bit but the climbs and descents on the way out were all fine in 2wd. Got to the viewpoint at the top, stopped to take a couple photos and look around. 15 min later we climbed back in and started the Jeep, put it in reverse and moved back about 10 feet on flat ground and the battery light came on in the cluster and dinged. Finished reversing and put the Jeep in Park and shut it off. It restarted without issue and battery light was off, alternator voltage was the normal 13.7-14.0ish. Headed back on the trail and on a steeper downhill section I slowed and went into 4Low so I didn't have to ride the brakes as much but it wasn't steep by any means. I had climbed it all in 2wd. I used Manual shift mode to keep it in first as we descended. As we continued the short downhill section the battery light comes on again, off, back on, repeatedly, at various intervals from a few seconds to over a minute with no discernable, repeatable cause. At this point I'm figuring we have the dreaded dead aux battery syndrome as the Jeep is ~2 1/2 years old from build date or maybe we have a loose fuse or battery terminal. We stop at the next convenient flat spot, shut down again, open the hood and pushed on all the fuses and relays, checked the main battery terminals, ground lugs, etc and nothing was loose or obviously wrong. Starts fine again and on back down the trail we go with no warning lights. Again in the steeper downhill sections I put it back 4L and the battery light comes on and off repeatedly, but it never happens on any of the short climbs, just the descents. On a longer (~400 yd) final descent it happened again several times and this time the check engine light comes on too. We stopped at the end to air up(engine running for that) and lock the sway bar back in and it started up again just fine, but still had the check engine light but no battery light. Got on the highway for the short 6-8 miles back to town, watching all the temps and voltage, and everything ran fine.
Long story longer, took it to a dealer this morning thinking it was for sure going to be the aux battery failing. They said they now have to do a 4-5 hour diagnostic test with a special tool that connects with Jeep Engineers. (Apparently Jeep was sick of dealers just replacing batteries left and right and that not actually being the issue.) After the test was complete they had found nothing wrong and the fault code was reset. Fault code was loss of communications to some part of the cooling system. We immediately headed back out to the scene of the crime to see if it was really fixed since it was only a few miles from the dealer. Didn't bother to air down this time but disconnected the sway bar and did the first 400yd climb in 4Low without issue or any warning lights. Turned around and came back down in 4Low as we had yesterday and sure as shit the battery light came back on and off several times. No check engine light this time though and the battery light never stayed on very long. Back to the dealer we go and I make them do the battery tests on both batteries with me watching, as they didn't have a record showing that they had actually tested them earlier in the day. Both batteries tested fine.
It hasn't happened on any flat roads, dirt or asphalt, 4Low, or otherwise. Where would I start looking for a likely culprit? I can't think of anything related to the transfer case actuator lever that would be anywhere near a battery lead or a wire with any significant load. The main battery is tight in the tray, not sure about the aux battery but don't hear any rattling in the front right while driving. Only electrical add on I have is a winch which has been on for almost the whole time and have wrapped those leads and checked them recently for any wear and there was none, and a short there would be a massive failure, not intermittent (yes I know I need to put a disconnect on it by the battery).
Open to any suggestions or productive thoughts on this. Still under factory warranty and the Jeep isn't a daily driver so I am tempted to just let my local dealer at home dig into it but not sure they would even bother to actually figure it out.
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