JLUR battery flatlining when flat towing

[JJT-NC]

A man's gotta do what a man's gotta do. Very clever work around but a bummer you had to resort to this. You are also resetting the ECU (and emissions monitors) each time the battery is disconnected. This may not be that troublesome overall but make sure you have the battery connected ~100 miles or more before you go in to an ECU-based smog test (if your state has that).

Thanks for the tip but no smog testing here!

I’m just doing what the software SHOULD be doing. Lots of great features in the jeep but critic fail on battery management design - the system should never allow a battery to discharge beyond what is needed for starting the engine. Period.

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[Terminex]

I am curious on the wiring for the cool tech vs the mopar. I know the mopar harness DOES use the red wire from the 7 pic that is the 12V charge lead.

I am wondering if that is somehow charging the battery while towing. (even though you only connect the harness to the tail lights & license plate light.)

I never liked the fact that the mopar harness is a "black box" in that they do not give you the actual wiring diagram.

 

[JimN]

I am about to embark on an extended trip. I will tow my JL and it will remain connected to the RV from Saturday morning until most likely Monday, at that point it will be driven maybe 100 miles, then reconnected to the RV where it will not be disconnected most likely for up to 4 days. After that there will be a day of towing followed by several days where the JL is in use repeated for about two months. I am going to rig my Dash Cam with a separate battery, not connected to the Jeep or the RV. I will have this aimed at the dash and the rear of the RV. If the Jeep remains asleep, the dash should not ever awaken until I open the Jeep to disconnect it. If it does wake, that would point to an issue, what the solution is or will be I don't know. I did add an RVi Toad Charger as I don't need o be killing my batteries. This addresses Issue #1.

Issue #2 is why does the Auto Start-Stop and Anti Skid service required light come on periodically? I read that a lot of stop and go driving is not 'proper use' of a Jeep. Really? What freaking genius would build a system like that? Let's not even discuss that this is a JEEP and is often used in places where there is very low going with lots of starts and stops, how about just driving around in normal every day traffic. And what team of geniuses designed a vehicle with two batteries, one of which takes three hours to change, being mounted UNDERNEATH the fuse blocks and power distribution panel?

 

[CoolTech]

JimN - A few questions if you don't mind....

1. What light wiring kit do you have and who installed?
2. Does your Jeep have the LED light option
3. Issue #2 - When does this randomly occur? Does it happen only after recently towing or just at random times not related to recently towing?

Have fun on your trip and drive safe!!

 

[JimN]

JimN - A few questions if you don't mind....

1. What light wiring kit do you have and who installed?
2. Does your Jeep have the LED light option
3. Issue #2 - When does this randomly occur? Does it happen only after recently towing or just at random times not related to recently towing?

Have fun on your trip and drive safe!!

I have the Blue Ox Diode Kit. I installed it.
I do have the LED light option
The Start-Stop issue is random. sometimes multiple in a day, sometimes not for a week or more.

 

[JimN]

I have the Blue Ox Diode Kit. I installed it.
I do have the LED light option
The Start-Stop issue is random. sometimes multiple in a day, sometimes not for a week or more. And this issue seems to have nothing to do with towing.

 

[Jgam]

Hello, following with great angst. I'm having the same problems with my 2018 JL. No auxiliary brake system and no charge wire. One full day of towing all good. Four days batteries flat , 3 days like 3.5 volts I checked , it won't even try to crank. I sure hope someone smarter than me figures this out. I hate putting patches on problems. My guess , it's gotta be something in the brake circuit. I'm tempted to go to harbor freight and get a cheap set of magnetic tow lights, then not even plug in the Jeep at all, tow it for four days just to see if the batteries are dead...

 

[JimN]

OK< here is where I am at with this. On shorter tows we seemed to be good, this year we did a few long tows and the dead battery issue reared its head. We have a 2018 JL Sahara with an Air Force One Braking system. This unit draws no power from the vehicle other than an LED indicator light when the brakes are applied. The lights are all run off diodes and powered off the tow umbilical. Apparently, even though Jeep says you do not need to do anything special, they have not actually towed one. It seems that the Jeep 'Wakes Up' and this puts a drain on the battery. I added a charge line with a Diode and then upgraded that to a RViToad Charger. This is a 'Smart' unit and only allows voltage through if needed and also will not over charge your toad. If you are using a portable brake or a built in electric you will need a charge line or a dedicated battery. So, back to the Jeep Waking Up. I will be taking a trip soon and I am planning on running my Jeep's Dash Cam from onside the Jeep powered by a dedicated battery, so I can see the dash of the Jeep and see if it stays off or if the thing wakes. Like many I too thought I had possibly left the Jeep in ACC mode. To those that have asked elsewhere, you do not need to leave the Jeep ON, nor do you need to leave the FOB in the vehicle.

 

[CoolTech]

The lights are all run off diodes

I'm really thinking the problem may be here... let me explain.

These generic, Chinese-made diode-based kits have been around forever and were intended to provide isolation to filament based lights that were essentially 2-wires, power and ground. The diode is installed on the power wire preventing current from traveling back into the Jeep electronics. OK, but many modern cars including the Jeep now have LED rear lights. There is now more than two wires going to the lights - there is a third, fault-sense wire. With a filament type bulb it was easy to detect a bulb-out situation. Any filament-based bulb has continuity across the positive and negative leads and when the filament fails, there is no more continuity. Easy to test/detect. With an LED it is not so easy. Now there is a circuit involved and the fault-sense wire is supplying feedback to the ECU regarding the functioning of the LED light. Long story short, this fault-sense wire is not being isolated - and it *could be* what is waking up the Jeep and causing the drain on the battery.

I was hoping that one of the owners with the problem could perform a test and help the community (and Jeep) to better understand the problem. If anyone was so inclined, here's my request.

1. Follow all of the Jeep recommended guidelines for attaching to the RV
2. Before exiting the Jeep, roll the driver's window down.
3. Have the RV running like you are ready to be on your way.
4. Wait about 5 minutes.
5. Reach in through the open driver's window and press the Jeep's brake pedal.
6. If the brake lights do not illuminate, the Jeep is asleep. (Good)
7. Now, inside the motorhome go press on the brake pedal a few times.... and then repeat Step 5
8. Is the Jeep now awake or still asleep?
9. If still asleep, try turning on the RV's parking lights and then repeat Step 5.
10. Results?

We are trying to determine what action causes the Jeep to come out of Sleep mode.

 

[JimN]

I'm really thinking the problem may be here... let me explain.

These generic, Chinese-made diode-based kits have been around forever and were intended to provide isolation to filament based lights that were essentially 2-wires, power and ground. The diode is installed on the power wire preventing current from traveling back into the Jeep electronics. OK, but many modern cars including the Jeep now have LED rear lights. There is now more than two wires going to the lights - there is a third, fault-sense wire. With a filament type bulb it was easy to detect a bulb-out situation. Any filament-based bulb has continuity across the positive and negative leads and when the filament fails, there is no more continuity. Easy to test/detect. With an LED it is not so easy. Now there is a circuit involved and the fault-sense wire is supplying feedback to the ECU regarding the functioning of the LED light. Long story short, this fault-sense wire is not being isolated - and it *could be* what is waking up the Jeep and causing the drain on the battery.

I was hoping that one of the owners with the problem could perform a test and help the community (and Jeep) to better understand the problem. If anyone was so inclined, here's my request.

1. Follow all of the Jeep recommended guidelines for attaching to the RV
2. Before exiting the Jeep, roll the driver's window down.
3. Have the RV running like you are ready to be on your way.
4. Wait about 5 minutes.
5. Reach in through the open driver's window and press the Jeep's brake pedal.
6. If the brake lights do not illuminate, the Jeep is asleep. (Good)
7. Now, inside the motorhome go press on the brake pedal a few times.... and then repeat Step 5
8. Is the Jeep now awake or still asleep?
9. If still asleep, try turning on the RV's parking lights and then repeat Step 5.
10. Results?

We are trying to determine what action causes the Jeep to come out of Sleep mode.

I am going to set up my Dash Cam with a dedicated battery to watch the dash over a 5 hour tow. I do know that the other day I took my Jeep to a car wash to wash the engine compartment and with the engine off and the doors all shut, on several occasions the lights and head lights all came on, similar to when one opens a door. Thinking SOMETHING is waking up the monster!

 

[Jgam]

I'm really thinking the problem may be here... let me explain.

These generic, Chinese-made diode-based kits have been around forever and were intended to provide isolation to filament based lights that were essentially 2-wires, power and ground. The diode is installed on the power wire preventing current from traveling back into the Jeep electronics. OK, but many modern cars including the Jeep now have LED rear lights. There is now more than two wires going to the lights - there is a third, fault-sense wire. With a filament type bulb it was easy to detect a bulb-out situation. Any filament-based bulb has continuity across the positive and negative leads and when the filament fails, there is no more continuity. Easy to test/detect. With an LED it is not so easy. Now there is a circuit involved and the fault-sense wire is supplying feedback to the ECU regarding the functioning of the LED light. Long story short, this fault-sense wire is not being isolated - and it *could be* what is waking up the Jeep and causing the drain on the battery.

I was hoping that one of the owners with the problem could perform a test and help the community (and Jeep) to better understand the problem. If anyone was so inclined, here's my request.

1. Follow all of the Jeep recommended guidelines for attaching to the RV
2. Before exiting the Jeep, roll the driver's window down.
3. Have the RV running like you are ready to be on your way.
4. Wait about 5 minutes.
5. Reach in through the open driver's window and press the Jeep's brake pedal.
6. If the brake lights do not illuminate, the Jeep is asleep. (Good)
7. Now, inside the motorhome go press on the brake pedal a few times.... and then repeat Step 5
8. Is the Jeep now awake or still asleep?
9. If still asleep, try turning on the RV's parking lights and then repeat Step 5.
10. Results?

We are trying to determine what action causes the Jeep to come out of Sleep mode.

Ok, I have performed the test. After going through all the towing procedures, hooked everything up like the Jeep manual says to I've figured out that the Jeep wakes up if the brake is applied or the turn signal is on in the coach. My 2018 JL will definitely need a charge wire. My system is using the roadmaster diode setup. Now I just need to decide if I'm taking it back to my installer to get my money back. Hope this helps ...

 

[Jgam]

Well, I decided to go back to my installer. I talked with Roadmaster and they have questions regarding the install process. Now the two of them can talk it out (my installer & Roadmaster) with my new information. Sure wish I'd gone with the CoolTech harness first.

 

[JimN]

I am going to set up my Dash Cam with a dedicated battery to watch the dash over a 5 hour tow. I do know that the other day I took my Jeep to a car wash to wash the engine compartment and with the engine off and the doors all shut, on several occasions the lights and head lights all came on, similar to when one opens a door. Thinking SOMETHING is waking up the monster!

So, results of the camera test. We as I think all do have the PB Start. There are thee areas where we would see light, the far left, the ACC and the RUN. While the full dash never lit up, the left most indicator on the Ignition switch did and it stayed lit for a considerable time, shut off occasionally and then relit. I would think that this could indicate that while be towed the vehicle is coming at least partially awake. I no longer have the dead battery issue as I installed the RZi Toad Charger. I do still get the Stability Control and Start/Stop in operative issue. At times. Sometimes just the Stability Track as in very hot weather the Start Stop function is apparently disabled.

 

[Jmonroe]

Just got back from a trip. On the way north the Jeep was towed 1200 miles over a few days without ever being disconnected. Batteries were totally flat when we got to our destination. I found the (older generation) toad charger was not connected (no fuse). It was towed for a few shorter trips while we were gone with no issue. Leaving Nashville, where we used the Jeep daily, we had two overnight stops on the way home and I never touched the Jeep, never disconnected. The toad charger should now be active. Batteries were dead when we got here.

For what it's worth, I'm using the Cooltech light harness.

I really hope someone can come up with a simple fix.

 

[Jgam]

Just got back from a trip. On the way north the Jeep was towed 1200 miles over a few days without ever being disconnected. Batteries were totally flat when we got to our destination. I found the (older generation) toad charger was not connected (no fuse). It was towed for a few shorter trips while we were gone with no issue. Leaving Nashville, where we used the Jeep daily, we had two overnight stops on the way home and I never touched the Jeep, never disconnected. The toad charger should now be active. Batteries were dead when we got here.

For what it's worth, I'm using the Cooltech light harness.

I really hope someone can come up with a simple fix.

Interesting, I didn't realize the CoolTech harness was having these issues. I sure hope we can come up with a solution to this issue.

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