SOLVED - Aux Battery Issue on the road - need help

[TMac99]

I initially posted this in electronics, but after some searching and reading, this seems to be the place to post it. I also have additional information from my original post.

I have a 2018 JL 3.6L that we use as a toad behind a motorhome. While driving the Jeep today, it would not start after the ESS shut the engine down at a stop. I had all kinds of error message and check engine lights. I was able to get it started with a jump from another vehicle. We were close to my camping site, so drove it back there (about 300 yards). On that drive I got a dash message that said something like “Pull over, Jeep will shut down soon“. Once I got to my camping site it ran rough and did shut down on its own. Gauges were flickering and wipers were going without being turned on. I tried jumping again (charging for 15 minutes before I tried), but the Jeep won’t even turn on. I measured the main battery at 12.9V and the aux was initially 10.1 volts but it did seem to rise after charging to over 12. Despite having 2 seemingly OK batteries, the Jeep is totally electrically dead. Will not turn on, lights won’t come on, nothing electrical works at all.

UPDATED INFO
After reading all the info I could find on the aux battery (thanks Jediruph - your info is awesome) I tried jumping posts N1 and N2. Vehicle started normally. Only anomaly I saw was that the charging volts were only 12.4 - way lower than I expected with a dead battery. As soon as I removed the temporary N1 to N2 jumper the engine quit. The jumper was not suitable to drive with, so I couldn’t drive it around. I borrowed a NOCO GB150 booster and left it connected for 15 minutes still totally dead. The batteries (individually measured by the GB 150) were 12.8 for the main and 13 for the aux.
So, it seems like both batteries are charged OK but nothing electrical (and I mean nothing) will show signs of life. (even the dome light). My only thought by looking at Jediruph’s great diagrams is that the PCR may be shorted open and that is preventing any Aux power from getting through. I tried to unplug the PCR, but although I can reach it, I can’t see it well enough to figure out how to release the plug.
Assuming it is a bad PCR, if I bypass it with an N1 to N2 jumper, is the Jeep safe to drive? We are 600 miles from home.
would I be better with the PCR unplugged (assuming I can figure out how to do that.).
Any other suggestions?
Thanks in advance for any and all help.

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[jeepdabest]

Why was the jumper not ok to drive with? Seems like you had the solution to get you home.

 

[TMac99]

Thanks to all the of Jediruph’s posts and a very kind live phone call from Rheinbeck, I am back in business. I was able to confirm that the Aux battery is dead. Using a voltmeter with a very rudimentary load tester, the Aux battery voltage measured at 12 but dropped almost instantly to 2 with the load applied.
It is still under warranty, so it will go to the Jeep dealer when I get home. In the mean time, with help from Rheinbeck, I installed a 40 amp fused jumper from N1 to N2 and disconnected the Aux battery negative terminal and taped it off. The Jeep started normally, but did have a “check engine” light on first start. That CEL went away on the second start and the Jeep seems to behave normally. Huge thanks to Rheinbeck for the live help and to Jediruph for all the work investigating, and more importantly, documenting clearly, the battery system. You guys “saved” my camping vacation.

 

[TMac99]

Why was the jumper not ok to drive with? Seems like you had the solution to get you home.

The temporary jumper was exactly that - I literally used a jumper cable to jump N1 to N2 and could not drive with that mess of wires in the way

 

[Rhinebeck01]

Thanks to all the of Jediruph’s posts and a very kind live phone call from Rheinbeck, I am back in business. I was able to confirm that the Aux battery is dead. Using a voltmeter with a very rudimentary load tester, the Aux battery voltage measured at 12 but dropped almost instantly to 2 with the load applied.
It is still under warranty, so it will go to the Jeep dealer when I get home. In the mean time, with help from Rheinbeck, I installed a 40 amp fused jumper from N1 to N2 and disconnected the Aux battery negative terminal and taped it off. The Jeep started normally, but did have a “check engine” light on first start. That CEL went away on the second start and the Jeep seems to behave normally. Huge thanks to Rheinbeck for the live help and to Jediruph for all the work investigating, and more importantly, documenting clearly, the battery system. You guys “saved” my camping vacation.

@TMac99

Good you got going and your camping vacation was not impacted to bad.

Glad I could be of help to you. Your call to me, got me out of the Sun for 15 minutes. I was out mowing when you called. 8-) Around 90 degress here in Upstate NY today.

I figured the Aux was dead and that isolating it properly and testing it would verify that.

Let us know how you make out at the dealer. I'm sure from now on, you will
keep that fused N1-N2 jumper in your JL at all times. Ya never know when you
might need it.. 8-)

 

[Jebiruph]

I initially posted this in electronics, but after some searching and reading, this seems to be the place to post it. I also have additional information from my original post.

I have a 2018 JL 3.6L that we use as a toad behind a motorhome. While driving the Jeep today, it would not start after the ESS shut the engine down at a stop. I had all kinds of error message and check engine lights. I was able to get it started with a jump from another vehicle. We were close to my camping site, so drove it back there (about 300 yards). On that drive I got a dash message that said something like “Pull over, Jeep will shut down soon“. Once I got to my camping site it ran rough and did shut down on its own. Gauges were flickering and wipers were going without being turned on. I tried jumping again (charging for 15 minutes before I tried), but the Jeep won’t even turn on. I measured the main battery at 12.9V and the aux was initially 10.1 volts but it did seem to rise after charging to over 12. Despite having 2 seemingly OK batteries, the Jeep is totally electrically dead. Will not turn on, lights won’t come on, nothing electrical works at all.

UPDATED INFO
After reading all the info I could find on the aux battery (thanks Jediruph - your info is awesome) I tried jumping posts N1 and N2. Vehicle started normally. Only anomaly I saw was that the charging volts were only 12.4 - way lower than I expected with a dead battery. As soon as I removed the temporary N1 to N2 jumper the engine quit. The jumper was not suitable to drive with, so I couldn’t drive it around. I borrowed a NOCO GB150 booster and left it connected for 15 minutes still totally dead. The batteries (individually measured by the GB 150) were 12.8 for the main and 13 for the aux.
So, it seems like both batteries are charged OK but nothing electrical (and I mean nothing) will show signs of life. (even the dome light). My only thought by looking at Jediruph’s great diagrams is that the PCR may be shorted open and that is preventing any Aux power from getting through. I tried to unplug the PCR, but although I can reach it, I can’t see it well enough to figure out how to release the plug.
Assuming it is a bad PCR, if I bypass it with an N1 to N2 jumper, is the Jeep safe to drive? We are 600 miles from home.
would I be better with the PCR unplugged (assuming I can figure out how to do that.).
Any other suggestions?
Thanks in advance for any and all help.

I don't hear of a lot of PCRs failing, but they do.

Here are some pics to help locating and unplugging it. It's on the passenger side of the firewall.

Have the dealer update your PCM, it should resolve the dead aux - no start issue.
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-bad-aux-battery-no-start-firmware-fix.53608/

 

[Jebiruph]

I initially posted this in electronics, but after some searching and reading, this seems to be the place to post it. I also have additional information from my original post.

I have a 2018 JL 3.6L that we use as a toad behind a motorhome. While driving the Jeep today, it would not start after the ESS shut the engine down at a stop. I had all kinds of error message and check engine lights. I was able to get it started with a jump from another vehicle. We were close to my camping site, so drove it back there (about 300 yards). On that drive I got a dash message that said something like “Pull over, Jeep will shut down soon“. Once I got to my camping site it ran rough and did shut down on its own. Gauges were flickering and wipers were going without being turned on. I tried jumping again (charging for 15 minutes before I tried), but the Jeep won’t even turn on. I measured the main battery at 12.9V and the aux was initially 10.1 volts but it did seem to rise after charging to over 12. Despite having 2 seemingly OK batteries, the Jeep is totally electrically dead. Will not turn on, lights won’t come on, nothing electrical works at all.

UPDATED INFO
After reading all the info I could find on the aux battery (thanks Jediruph - your info is awesome) I tried jumping posts N1 and N2. Vehicle started normally. Only anomaly I saw was that the charging volts were only 12.4 - way lower than I expected with a dead battery. As soon as I removed the temporary N1 to N2 jumper the engine quit. The jumper was not suitable to drive with, so I couldn’t drive it around. I borrowed a NOCO GB150 booster and left it connected for 15 minutes still totally dead. The batteries (individually measured by the GB 150) were 12.8 for the main and 13 for the aux.
So, it seems like both batteries are charged OK but nothing electrical (and I mean nothing) will show signs of life. (even the dome light). My only thought by looking at Jediruph’s great diagrams is that the PCR may be shorted open and that is preventing any Aux power from getting through. I tried to unplug the PCR, but although I can reach it, I can’t see it well enough to figure out how to release the plug.
Assuming it is a bad PCR, if I bypass it with an N1 to N2 jumper, is the Jeep safe to drive? We are 600 miles from home.
would I be better with the PCR unplugged (assuming I can figure out how to do that.).
Any other suggestions?
Thanks in advance for any and all help.

In an emergengy, temporarily connecting N1 to N2 with any wire should work. The lack of a fuse is mostly an issue when the positive terminal is disconnected due to possible shorting it to ground. In your situation, unplugging the PCR if you can is probably the best choice.

 

[Rhinebeck01]

@Jebiruph

I mentioned to @TMac99 about the pcm update you are speaking about.

I have been holding off on having that pcm update done til I hear how others are impacted negatively or positively b yupdate.

I know what I am working with now so to speak. After a few here get the update done and they report here, I'll lets say think about it. 8-)

Unplugging the PCR is not an easy deed for many... Looks really accessible in the pic you posted with fender/liners off. 8-)

Probably just a dead Aux .... guessing like us all. We'll see what the dealer says.

 

[Jebiruph]

@Jebiruph

I mentioned to @TMac99 about the pcm update you are speaking about.

I have been holding off on having that pcm update done til I hear how others are impacted negatively or positively b yupdate.

I know what I am working with now so to speak. After a few here get the update done and they report here, I'll lets say think about it. 8-)

Unplugging the PCR is not an easy deed for many... Looks really accessible in the pic you posted with fender/liners off. 8-)

Probably just a dead Aux .... guessing like us all. We'll see what the dealer says.

I agree the PCR is not an easy unplug, but it can save someone without a workable jumper.

No issues with my PCM update, but not driving enough to really test. With the update and clutch recall, my JL is running better than ever.

 

[Rhinebeck01]

@Jebiruph

Wish I was up to speed on this battery(2) crapola a year and a half ago when the Tazer JL depleted my Aux battery and let me in a lurch in Newport Rhode Island.

I've learned lots about the JL since I acquired mine in May 2018.

I didn't know all we now know about jump starting the JL, the N1 - N2 jumper, the PCR disconnect, Batteries depleting if the JL sits for a few weeks, etc.

Guess we early adopters/buyers of the JL broke some ground so to speak, that is helping not only us, but a lot of new JL and JT owner's now a days.

When I read @TMac99 's post here today, saying HELP, I had a flash back.... I remembered how distraught I was when my Rubi had a similar issue and tried to leave me high and dry when I was on a trip.... My Tazer JL had caused depletion of my Aux battery. I remember how I had to tell the FAC sent Tow guy how to jump my JL...... he did not know how.... good thing I had done some homework when I first got the JL.

Anyway, I reached out to TMac, via forum messaging and said call me, so I can get you going.... I did not want to see him go through to much grief.

I have to give Tmac99 a lot of credit. Most guys would come here asking for help before reading forum posts here and trying to figure it out for themselves. Tmac99 had already done his homework so to speak. I just added on a few tidbits lets say, like how to isolate the Aux so it could be tested, some reassurance and a bit more... 8-)

 

[Big Hoss]

@Rhinebeck01

How did the Tazer kill your battery? (I have one installed and wondered if that's what killed my aux battery 2 weeks ago).

 

[Rhinebeck01]

@Rhinebeck01

How did the Tazer kill your battery? (I have one installed and wondered if that's what killed my aux battery 2 weeks ago).

@Big Hoss

When Joe, first came out with the Tazer JL, there were a few different quirks lets say. Can tell you that those quirks were addressed/remedied many months ago with new firmware that Joe made available..

Hint: In regard to the Tazer JL, Tazer JL Lite and the Tazer JL Mini, always make sure you are running the most current firmware.

 

[Big Hoss]

Thanks for the info. I have the latest firmware in the JL mini I have installed.

 

[GCJCTC2]

@TMac99

Good you got going and your camping vacation was not impacted to bad.

Glad I could be of help to you. Your call to me, got me out of the Sun for 15 minutes. I was out mowing when you called. 8-) Around 90 degress here in Upstate NY today.

I figured the Aux was dead and that isolating it properly and testing it would verify that.

Let us know how you make out at the dealer. I'm sure from now on, you will
keep that fused N1-N2 jumper in your JL at all times. Ya never know when you
might need it.. 8-)

Can someone please explain exactly what a “fused N1 to N2 jumper” is and how to use it properly”? Sounds like I need to keep one in my 2018 JLU Sport S!!

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