[SOLVED] JLU Completely dead in traffic / dash freakout

[jantman]

I have a 2019 JLU Moab daily driver, pretty much stock, 33,900 miles, 39 months old.

About a month ago I started getting the "Auxiliary Switches Temporarily Disabled" message. Honestly just ignored it, figuring I'd deal with it at my next service interval. Two weeks ago it failed to start. Sorta freaked out (3 years is still "new" in my mind), did a bunch of research here and elsewhere, and came away with the conclusion that I'd try throwing it on a battery charger and see how it goes. Bought a charger and a new jump pack (hadn't used mine in years and it was dead as a stone), put it on the maintenance charger overnight with all connections left as factory (i.e. charging both batteries, for better or worse). Started and ran fine the next morning, and for the next two weeks.

... until yesterday (Saturday). Fine in the morning, but spent the morning doing a bunch of local errands, lots of short trips. About noon, wouldn't start, had to jump it. Figured I'd deal with it tomorrow (Monday). Just left my last stop for the day, it started fine, and about a mile down the road I was in traffic at a red light and when I let off the brake when the light changed, the engine stopped. Dash went absolutely crazy lighting up all sorts of lights, flashing the cabin lights, the "Stop Safely Vehicle Will Shut Off Soon" message, etc. Managed to get it jumped again (dash still going crazy) and pull into the next parking lot. Engine started knocking then died. Sat there through the death throes, dash going crazy, not a single button working, couldn't turn it off, cabin lights blinking, windows stuck down. Had it flat-bedded home figuring I needed to replace the battery (aux or both).

After leaving it on a charger overnight it was still completely dead this morning, 100% lifeless.

So today, after a lot more serious reading of older threads on here and some investigation, and reading through the mostly useless electrical section of the service manual, I've determined that (1) my cranking battery is on its way out and won't hold a charge beyond 12.4v, (2) my aux battery is completely shot, and (3) fuse N3 on the Z-case fuse assembly was blown. I swapped the lead from N3 to N4 (unused) and with the assistance of a jump pack was able to power it on enough to roll up the windows, lock the doors, and get the mileage. Wasn't brave/stupid enough to try to start it.

So... it's freshly out of factory warranty. My dealer couldn't care less about me, never has. I bought (50% stupidity/50% was misled) an extended service contract, but that of course doesn't cover batteries or fuses. My current plan is to buy a new aux battery tomorrow, charge it up, swap it in, and see if that makes everything more or less happy. When I do that, I'll get the part number (of course I forgot to earlier) of the Z-case fuse and order a replacement (or two). If the cranking battery still seems weak after another maintenance charge, I'll replace that too.

Am I missing something important here, or being short-sighted? After all the stories I've seen on here of dealers keeping a vehicle for a week and doing nothing but replacing the batteries and maybe the Z-case fuse (if I'm lucky, and whole PDC if I'm not), I figure that if I buy the batteries from the dealer, worst comes to worst it doesn't help and I get it towed there and at least the batteries are brand new and they won't try that...

And, am I being a complete idiot thinking about replacing with OEM batteries?

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[Dp227]

The battery isn’t the worst starting idea. You done a code scan yet? Stupid question here but do you think you could have gotten bad gasoline?

 

[Al G]

When mine did that the dealer also replaced an electronic module along with the batteries. New batteries alone may not solve your root problem.

 

[jantman]

The battery isn’t the worst starting idea. You done a code scan yet? Stupid question here but do you think you could have gotten bad gasoline?

Definitely not bad gas, for many reasons. I haven't done a code scan because it's been DEAD. As in, not a single light anywhere. As dead as if every inch of wire was ripped out of it. Switching N3 to N4 got me enough power (with jump pack) to roll up the windows, but even those weren't acting right, the motors had a rather regular oscillation in speed (i.e. a pulsing).

 

[JABCAT]

Batteries are the first thing I would replace when my vehicle doesn't start. They are wear items & if you live in warmer/hotter climates, they tend to wear out faster. I'd also recommend keeping your vehicles on a battery maintainer.

 

[Bkilby]

I'd charge the battery back up if you can, then put it under a load test. (Harbor Freight, $20). A better quality tester would be better though. If you charge the battery but it fails a load test, that just means you have limited life of the battery and you need to replace it. You can't get a good reading with a load tester if the battery hasn't been charged though.... And after 3 years on a stock battery, I'd just replace it anyhow because it's just a matter of time. I personally like Deka batteries.

 

[jantman]

I'd charge the battery back up if you can, then put it under a load test. (Harbor Freight, $20). A better quality tester would be better though. If you charge the battery but it fails a load test, that just means you have limited life of the battery and you need to replace it. You can't get a good reading with a load tester if the battery hasn't been charged though.... And after 3 years on a stock battery, I'd just replace it anyhow because it's just a matter of time. I personally like Deka batteries.

Thanks. I charged (as best it could take) and load tested the aux, and it failed miserably. It charged up to ~14v and after a 10-second 100A load test was down to 6v. The load test (Schumacher analog unit) barely got to the "bad" level.

Unfortunately, it looks like *nobody* around me carries the 200A Group 400 aux batteries. I'll call the local dealers in the morning.

 

[Chris2183]

At 18 months mine died on me in an intersection the first time. I was able to jumpstart it and get it home.

Replaced the main battery and after a few days it wouldn't start. Jumped out the aux battery and was able to drive it again.

Replaced aux battery and the Jeep has been fine ever since. I do suspect that its getting close to the time to replace one or both again, however I just sold it yesterday so I will never know.

 

[YippieKiYayMrFalcon]

I think the general thought is if you get to the point where the jeep died in traffic, you should probably go ahead and replace both batteries. A bad one can bring down the other.

Also, I recommend replacing the aux by going through the fender. Not a good idea to remove the PDC. If you do remove the fender, it’s good to have a few of the clips laying around, as you’ll likely break a few.

https://www.mymoparparts.com/oem-parts/mopar-w-type-clip-68526185aa

 

[jantman]

I think the general thought is if you get to the point where the jeep died in traffic, you should probably go ahead and replace both batteries. A bad one can bring down the other.

Also, I recommend replacing the aux by going through the fender. Not a good idea to remove the PDC. If you do remove the fender, it’s good to have a few of the clips laying around, as you’ll likely break a few.

https://www.mymoparparts.com/oem-parts/mopar-w-type-clip-68526185aa

Yeah, agreed, thanks. Also definitely agreed about the fender. I *do* have the service manual and that's the "official" procedure. I've got an assortment of trim clips, but wasn't prepared for them actually using what appear to be permanent rivet clips to attach the outer edge of the liner to the fender. Lucky for me, only 2 of about 8 were actually through the liner!

I left the main on the charger overnight. When I put it on, the charger went into desulfation mode. Got up this morning, charger thought it was ok. Put a load test on it and "bad" didn't even come close... under load, the needle barely moved from the bottom of the scale. Let the load off, and it shows voltage as 8... 9... 10... slowly climbing back.

So, slightly changed plan in the light of day. There's an O'Reilly less than a mile from home. They have both batteries in stock. Forget paying the dealer parts tax for batteries, I'll get them at O'Reilly, charge them up, put them in. Leave N3 cable moved to N4 and see how it does starting, and then a bit of driving around the neighborhood, and then going a bit farther (but sticking to relatively quiet roads for a while). I'll try to remember to disable ESS for the first couple of drives, just to be safe.

Then I'll see if I can find a dealer in the area with the Z-case fuse array in stock (68368854AA) and if I'm in luck, pick up two of them.

 

[Rhinebeck01]

There is a very good chance you will not need a replacement Mopar Z Case Fuse Array.

If you decide you do though, read at the link below before purchasing/installing one.

(It is a good idea to keep the correct Mopar Z Case Fuse Array / high amp fuse array on hand. I keep a backup in my JL)

https://www.jlwranglerforums.com/forum/threads/alert-high-amp-fuse-array-related.65085/

 

[jantman]

There is a very good chance you will not need a replacement Mopar Z Case Fuse Array.

If you decide you do though, read at the link below before purchasing/installing one.

(It is a good idea to keep the correct Mopar Z Case Fuse Array / high amp fuse array on hand. I keep a backup in my JL)

https://www.jlwranglerforums.com/forum/threads/alert-high-amp-fuse-array-related.65085/

Thanks. I definitely do; I've checked every fuse in it with a meter, and N3 is blown (open circuit / infinite resistance). Swapping the cable from N3 to (unused) N4 got me from completely dead to having power. I read that thread yesterday and REALLY appreciate it; it prompted me to pull my fuse array back out and take the actual part number from it, and sure enough, I have the 54AA (100A fan fuse). My closest dealer has one in stock and is holding it for me... so once the main battery is done charging, I'll head over there. If it fails to start, at least it'll do that in a precious parts counter parking space

 

[jantman]

Oh, one note... *nobody* has the 200 CCA AUX14 battery. Nobody. Everywhere I checked around me only has a 180CCA AUX12. So, we'll see how that does. Fingers crossed.

 

[Rhinebeck01]

.

Oh, one note... *nobody* has the 200 CCA AUX14 battery. Nobody. Everywhere I checked around me only has a 180CCA AUX12. So, we'll see how that does. Fingers crossed.

Don't go with an Aux 12..

For -- Aux battery replacement:

DieHard Platinum AGM Battery, BCI Group Size 400, 200 CCA
Part # AUX14-1

Super Start Platinum Auxiliary Battery Group Size 400
Part #AUX14

Braille (Part# B14115) I5Ah 360CCA
Tests from factory at 483 Crank Amps. Wt. 11.5 lbs.
https://www.jlwranglerforums.com/fo...-way-pull-the-fender-flare.56807/post-1911638

 

[engineXI]

until yesterday (Saturday). Fine in the morning, but spent the morning doing a bunch of local errands, lots of short trips. About noon, wouldn't start, had to jump it. Figured I'd deal with it tomorrow (Monday). Just left my last stop for the day, it started fine, and about a mile down the road I was in traffic at a red light and when I let off the brake when the light changed, the engine stopped. Dash went absolutely crazy lighting up all sorts of lights, flashing the cabin lights, the "Stop Safely Vehicle Will Shut Off Soon" message, etc. Managed to get it jumped again (dash still going crazy) and pull into the next parking lot. Engine started knocking then died. Sat there through the death throes, dash going crazy, not a single button working, couldn't turn it off, cabin lights blinking, windows stuck down. Had it flat-bedded home figuring I needed to replace the battery (aux or both).

Sounds like you've got a poltergeist in your jeep. First make sure you are not parking over any Indian burial grounds as those increase the power and frequency.

Next, since you mentioned your N3 fuse was open, I would suggest there is a reason for this. Maybe tracing it upwards to find out what components in the N3 circuit could be faulty. Those items may have been the root cause of your battery failure and would then be covered under your extended warranty to have them replaced as well as a new battery.

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