Yet another ESS thread - not a battery issue

[Bob Burd]

Before you start poking around on individual wires, first see if you have a parasitic drain. Disconnect the negative battery cables and separate them (one is ground, the other is negative of small battery). Connect one end of the ammeter (DC current on your multimeter) to ground, the other to the main battery negative (leave the aux battery negative disconnected). Let the car sit for about 10min or so and watch the current reading. Mine goes down to about 120mA when all is quiet. I don't know if that is normal, but anything above 200mA, I would suspect unwanted current drain.

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[TravelingJeff]

The PDC (Power Distribution Center) is the fuse box, found under the hood between the main battery and the firewall. Since the dealer swapped the aux (or said they did) there could still be a bent pin in there if they did it from the top. You can either take it back to the dealer and see if they can fix it, or check for the issue and fix it yourself, depending on your skill and confidence level. It's not that hard, but a mistake could mean a blown N1-N7 fuse array or further damage.

It's also possible that when you replaced the main battery that you did not reconnect the BMS (Battery Maintance Sensor) or that you crossed or failed to connect one of the grounds.

Thank you for the clarification. As per my original post, I have already confirmed no blown fuses in the N1-N7 array via multimeter. Dealer confirmed they swapped the battery through the fender.

I've never heard anyone use the acronym of "BMS", but it sounds like the same thing I've seen people refer to as "IBS" which attaches to the negative terminal. I did indeed reconnect this. I left the entire ground assembly connected and only removed the connector from the battery post, and reinstalled it as is to the new battery. (minus the negative lead to the aux battery which I wrapped in electrical tape and tucked away to delete the aux from the system). Seeing as I did not disconnect any other ground sources, I cannot think of any way I could have crossed or failed to connect a ground.

 

[Buddy Lee]

I see so many posts on the ESS topic. I just removed the Aux battery and all of the wiring including the PCR. I removed it 8 months ago and never looked back. No idiot lights and everything works flawlessly. The Jeep now runs on one H7 battery like it should have from the factory. I use an auto/stop/start to disable the ESS button so it never comes on. Only took a few hours to remove.

 

[TravelingJeff]

I see so many posts on the ESS topic. I just removed the Aux battery and all of the wiring including the PCR. I removed it 8 months ago and never looked back. No idiot lights and everything works flawlessly. The Jeep now runs on one H7 battery like it should have from the factory. I use an auto/stop/start to disable the ESS button so it never comes on. Only took a few hours to remove.

I would love to do this, but warranty

 

[Rhinebeck01]

I would love to do this, but warranty

Smart/prudent move on your part.

For a host of reasons, I believe an owner is far far better off leaving the Aux battery in place and not deleting it. Better to bypass it and install a quality H7 AGM battery... and to minimize use of the ESS feature.

Now, if you are an owner that can justify a pricey dual battery kit (most are not) then yes, have at it but I would not do to after warranty was over...

 

[Buddy Lee]

I totally get the warranty issues, especially if you have the extended one. I just decided to take ownership myself and avoid the dealership unless something catastrophic occurs. That is the only way I would end up there. They always seem to always find a way to deny warranty issues these days anyway.

 

[Buddy Lee]

Out of curiosity factory warranty aside, why would you be against it? I have absolutely zero issues. What are the cons it can create in your opinion?

 

[Rhinebeck01]

Out of curiosity factory warranty aside, why would you be against it? I have absolutely zero issues. What are the cons it can create in your opinion?

Pretty obvious to most.. You bastardize any factory electrical and you open up a whole can of beans. Tech won't/can't work on it as he is clueless what the fruck you did electrical wise. Tech's WiTechll shop computer can no longer do the deed as it can't interpret what it sees.... Any thing a Service Manager can use he uses when the chitt hits the fan so to speak.. the list goes on and on. AND you negatively impact your resale of your vehicle when you bastardize in excess.. especially bastardizing the electrical.

Misconception is that you install an aftermarket, dual battery system and all is peachy ... no maintenance or ever any dual battery related issues that would carry over to / cause issues with the JL in general.

Great that so far you have not had any issues... you will... I am that sure.

The aftermarket dual battery system is what it is.. Terrific and a way to go for some but for the masses lets say, no.. as it is costly overkill. And if you are a guy or gal that does not maintain any (stock or aftermarket) the chitt will hit the fan sooner or later..

No point in going back and forth on this. To each his own.

 

[Buddy Lee]

Pretty obvious to most.. You bastardize any factory electrical and you open up a whole can of beans. Tech won't/can't work on it as he is clueless what the fruck you did electrical wise. Tech's WiTechll shop computer can no longer do the deed as it can't interpret what it sees.... Any thing a Service Manager can use he uses when the chitt hits the fan so to speak.. the list goes on and on. AND you negatively impact your resale of your vehicle when you bastardize in excess.. especially bastardizing the electrical.

Misconception is that you install a dual battery system and all is peachy ... no maintenance or ever any dual battery related issues that would carry over to / cause issues with the JL in general.

Great that so far you have not had any issues... you will... I am that sure.

The aftermarket dual battery system is what it is.. Terrific and a way to go for some but for the masses lets say, no.. And if you are a guy or gal that does not maintain any (stock or aftermarket) the chitt will hit the fan sooner or later..

No point in going back and forth on this. To each his own.

Agreed, you are clearly the expert.

 

[UncleJimmy]

I did not replace the bottom battery, only the top. I'm not sure what the "PDC" is. I only replaced the top battery by disconnecting the old one, and re-connecting the new one, so I'm not sure what I could have bent. Do you have any pictures of what you are referring to, or would this not apply based on my reply?


Ah, so you're saying just swap the harnesses and not the positions of the plungers themselves? I noticed one of my plungers is "taller" than the other. They are nice and snug, and do slide easily as this is still a fairly new vehicle. Less than a year old and less than 15k miles

Swap the sensors themselves (my harness would not swap due to length), but either way - same thing. (And/or clean and lubricate or replace with new - the basic idea is the same). Those sensors are cup shaped and any muddy water or dirt will fill up the "plunger cup" and cause it to malfunction, which gives the "A" light.

However, if you don't want ESS and you have confirmed that this is the source of the issue and you have no other faults, then go ahead and leave it disconnected or leave the faulty hood sensor there. That way no additional costs or complexity, don't have to push the A button, and easy to reconnect if you so choose.

As I mentioned, I accomplish the same things by driving the auto transmission in manual selectable mode. This gives me the option to use ESS when i want (it also allows me to improve my mpg by about 2 mpg by shifting earlier or forcing it to hold 8th gear).

A few misc thoughts:

Regarding warranty, I have battery delete and taken in for warranty work (wheel sensor). They did not notice or care about aux battery because the system works perfectly as designed. After all, in general a dual or multi battery function as a single "battery system". So I don't worry about it unless I was specifically taking the vehicle in for battery or general electrical gremlins. However if you have more concern than me about warranty then the best option is just bypass the AUX as I believe you said you did. Just take the 5 mins to reconnect it before you take it back in. And obviously trickle charge it occasionally to keep it charged. (Not worth the hassle to me).

 

[TravelingJeff]

Swap the sensors themselves (my harness would not swap due to length), but either way - same thing. (And/or clean and lubricate or replace with new - the basic idea is the same). Those sensors are cup shaped and any muddy water or dirt will fill up the "plunger cup" and cause it to malfunction, which gives the "A" light.

However, if you don't want ESS and you have confirmed that this is the source of the issue and you have no other faults, then go ahead and leave it disconnected or leave the faulty hood sensor there. That way no additional costs or complexity, don't have to push the A button, and easy to reconnect if you so choose.

As I mentioned, I accomplish the same things by driving the auto transmission in manual selectable mode. This gives me the option to use ESS when i want (it also allows me to improve my mpg by about 2 mpg by shifting earlier or forcing it to hold 8th gear).

A few misc thoughts:

Regarding warranty, I have battery delete and taken in for warranty work (wheel sensor). They did not notice or care about aux battery because the system works perfectly as designed. After all, in general a dual or multi battery function as a single "battery system". So I don't worry about it unless I was specifically taking the vehicle in for battery or general electrical gremlins. However if you have more concern than me about warranty then the best option is just bypass the AUX as I believe you said you did. Just take the 5 mins to reconnect it before you take it back in. And obviously trickle charge it occasionally to keep it charged. (Not worth the hassle to me).

If I leave it disconnected, then won't I get a dash alert about an open hood, or some other error from the missing sensor data?

 

[UncleJimmy]

If I leave it disconnected, then won't I get a dash alert about an open hood, or some other error from the missing sensor data?

You would get a message and light on dash - but my point is to diagnose the problem first, confirm that your issue was the same as mine and if it is then you know your system is working and you have no other problems to worry about. THEN, if you choose to disable ESS and don't want the cost and inconvenience of other methods then you have the option.

 

[TravelingJeff]

Gotcha. After switching the sensor positions, I was able to take two 1.5 hour drives with no A! light!!!!!

Since my voltage has been fluctuating correctly confirming a good battery, this is the first time I've seen everything work correctly since the first time the AUX battery died. I'll continue to monitor and post back here if anything changes, but so far, it looks like simple swapping the position of the hood sensors has solved my issue!

What a crazy situation.

 

[UncleJimmy]

Glad it worked for you!

 

[Dewey7015]

Hopefully this is my problem also...was in the middle of a 3 hour drive, in the rain.
I had pulled the fuse, and isolated the ground to ess about 9 months ago...
I was shocked when I got the "ess not ready" message, and the avengers symbol...lol.
Now I have hood open warning..
It looks like a simple 2 pin connection on those plungers..gonna try some dielectric grease..

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