3.6L ESS Aux Battery Bypass

cbrenthus

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I have looped N1 and N2 with a fused jumper and then removed the ESS negative off the main and my JL has started and ran fine with no error messages, I left it that way for just over a week and all was good, was going to leave it permanent but it’s under warranty so I just carry the jumper
Yes, I was going to do that bu instead unplugged the PCR relay - accomplishes the same goal of running solely on the main battery with no error messages.

But, when people talk about using the jumper for jump starting, there is no need as both batteries are in parallel when the engine is off - just connect cables and jump as normal. Or, if you don't want the aux battery pulling current and voltage from the donor, just disconnect it's negative.

What am I missing when people talk about installing the jumper to jumpstart?





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WranglerMan

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Yes, I was going to do that bu instead unplugged the PCR relay - accomplishes the same goal of running solely on the main battery with no error messages.

But, when people talk about using the jumper for jump starting, there is no need as both batteries are in parallel when the engine is off - just connect cables and jump as normal. Or, if you don't want the aux battery pulling current and voltage from the donor, just disconnect it's negative.

What am I missing when people talk about installing the jumper to jumpstart?
I may be incorrect but I believe that the JL will not start if the ESS battery is depleted even though the main has enough voltage so by jumping between N1 and N2 and disconnecting the ESS negative you are fooling it into the ESS having the correct starting voltage but like I said I may be wrong so maybe @Jebiruph can chime in and clarify
 

cbrenthus

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I may be incorrect but I believe that the JL will not start if the ESS battery is depleted even though the main has enough voltage so by jumping between N1 and N2 and disconnecting the ESS negative you are fooling it into the ESS having the correct starting voltage but like I said I may be wrong so maybe @Jebiruph can chime in and clarify
I thought that was the case as well, but after playing with the system and reading more, my understanding is that the PCR isolates the batteries during the startup process momentarily to check the Aux voltage, but only to see that the Aux battery is valid for ESS. I'm currently running with my Aux battery disconnected at the negative terminal, and everything works fine, but I get an ESS error after starting and then the orange ESS light stays on. Maybe they changed something in the ECM and older versions wouldn't start, but now they just disable ESS?

The other issue is that if the Aux battery is dead, its highly unlikely the main will be good because the Aux will take the main down with it since they are in parallel when the engine is off. In this case, if you try to jump the battery, both batteries will be pulling current and it will take it longer than normal to get enough voltage to start. You can disconnect the Aux to make it go quicker, but you'll get an ESS error upon start, or you can put the jumper in place if you don't want the error, but if you just had to jump the jeep who cares?
 

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Are the FCA dealers allowed to remove the aux battery, and return the system to a one battery operation. I have had it with ESS !!!!!!!!
 

cbrenthus

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Are the FCA dealers allowed to remove the aux battery, and return the system to a one battery operation. I have had it with ESS !!!!!!!!
Doubtful - but it's not hard to do. If you don't mind an error message when you start, and a yellow light when running just remove the Aux negative terminal. Done - no more ESS and or Aux battery BS.

If you don't want the error, you have to unplug the PCR, which is behind the passenger fender. ESS will still work, just running off the main battery, and you'll need a smart start/stop or Tazer if you want to disable ESS permanently.
 

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Doubtful - but it's not hard to do. If you don't mind an error message when you start, and a yellow light when running just remove the Aux negative terminal. Done - no more ESS and or Aux battery BS.

If you don't want the error, you have to unplug the PCR, which is behind the passenger fender. ESS will still work, just running off the main battery, and you'll need a smart start/stop or Tazer if you want to disable ESS permanently.
would installing a jumper at N1 and N2 and disconnect the ESS negative do the same as in no light or messages, the reason I ask is I installed my jumper and disconnected the ESS negative at the main and use a Smart Stop/Start module to disable ESS and never got an messages
 

cbrenthus

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would installing a jumper at N1 and N2 and disconnect the ESS negative do the same as in no light or messages, the reason I ask is I installed my jumper and disconnected the ESS negative at the main and use a Smart Stop/Start module to disable ESS and never got an messages
Yes, that is correct. Both the jumper and unplugging the PCR have the exact same affect of keeping the batteries in parallel at all times, so the ECM would not realize that one is disconnected because it sees the same voltage on both circuits.

The PCR is the relay that isolates the batteries. When you unplug it, the ECM thinks its telling the PCR to separate the batteries, but the PCR is not receiving the signal to isolate, thus the ECM still sees voltage on both circuits and thinks the Aux must be hooked up and is good.

The jumper accomplishes the same result by feeding voltage from the main circuit to the Aux circuit, so that even when the PCR isolates them, they are still connected.
 

cbrenthus

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Oh, by the way, I've tried several fuses to try to disable the PCR easily, all to no avail.
 

WranglerMan

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Yes, that is correct. Both the jumper and unplugging the PCR have the exact same affect of keeping the batteries in parallel at all times, so the ECM would not realize that one is disconnected because it sees the same voltage on both circuits.

The PCR is the relay that isolates the batteries. When you unplug it, the ECM thinks its telling the PCR to separate the batteries, but the PCR is not receiving the signal to isolate, thus the ECM still sees voltage on both circuits and thinks the Aux must be hooked up and is good.

The jumper accomplishes the same result by feeding voltage from the main circuit to the Aux circuit, so that even when the PCR isolates them, they are still connected.
Oh, by the way, I've tried several fuses to try to disable the PCR easily, all to no avail.
I may try to run my jumper and disconnected ESS negative long term to see if there are any ill effects
 

tablerock

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If the aux battery is disabled would it freeze and leak battery acid ???? Thanks
 

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I'm going to toss a damn hand grenade in the engine compartment and see what happens. That should do it.
 

MadDog27

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I'm going to toss a damn hand grenade in the engine compartment and see what happens. That should do it.
Not sure the warranty would cover that! :LOL:
 
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Jebiruph

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Yes, that is correct. Both the jumper and unplugging the PCR have the exact same affect of keeping the batteries in parallel at all times, so the ECM would not realize that one is disconnected because it sees the same voltage on both circuits.

The PCR is the relay that isolates the batteries. When you unplug it, the ECM thinks its telling the PCR to separate the batteries, but the PCR is not receiving the signal to isolate, thus the ECM still sees voltage on both circuits and thinks the Aux must be hooked up and is good.

The jumper accomplishes the same result by feeding voltage from the main circuit to the Aux circuit, so that even when the PCR isolates them, they are still connected.
Sorry I missed all the activity on this thread, I was busy buying a Gladiator.

@cbrenthus , I think you're mostly right on everything. Unplugging the PCR is mostly the same as using the jumper. But if the ESS high capacity fuse is blown, unplugging the PCR won't help, but the jumper will. The jumper also makes it easier to go back and forth by just installing/removing the fuse as opposed to crawling under the jeep to unplu/plug in the PCR.

The problem the fused jumper solves is when a bad aux battery can't be jump started. Early on, people were getting towed to the dealer for a dead battery. It wasn't until several months later that it was found that unplugging the PCR could also work. Since I have a fused jumper, I still prefer the jumper as opposed to crawling underneath to unplug the PCR.
 

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@Jebiruph you said “out buying a Gladiator” so I’m sure it has ESS the same as the JL but is it designed any better ?
 
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Jebiruph

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@Jebiruph you said “out buying a Gladiator” so I’m sure it has ESS the same as the JL but is it designed any better ?
I don't know yet, but I've been on the Gladiator forum and I'm not seeing the issues/complaints like I do here.
 

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