Jumperless aux battery/PCR bypass

jebiruph

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I was looking at the fuse descriptions on the underside of the PDC cover and saw this - F42 PCR CTRL FEED (ESS)*. Removing this fuse defeats the cold start aux battery test and allows the aux battery to be disconnected without generating any errors.

Unplugging the PCR has always been an alternative to using an N1 N2 fused jumper, both methods defeat the aux battery pass/fail test that occurs prior to a cold start. Unlike using a jumper, unplugging the PCR doesn't require any additional parts, it's just not easy to get to the PCR plug. Removing the F42 fuse accomplishes the same thing as unplugging the PCR, both actions prevent the PCR from activating and separating the batteries.

Here's the underside of the PDC cover showing the description and location of the fuse.
pcr-fuse-pdc-jpg.jpg



Here's the fuse location with the fuse removed.
pcr-fuse-pdc-2-jpg.jpg



Here's the schematic showing the fuse in the circuit.
pcr-fuse-2-jpg.jpg

 

CJXJJT

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Not being a smartass, school me here, why would I want to do this?
 
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jebiruph

jebiruph

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Not being a smartass, school me here, why would I want to do this?
The aux battery gets blamed for many issues and people talk about wanting to eliminated it, pulling the fuse lets you disconnect it with any errors.
 


dcmdon

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Does this mean that if one battery fails it is more likely to bring the other battery down?

Would a reasonable mod to go with this is simply remove the Aux battery and turn off ESS with a Tazer or AlfaOBD??
 

Lunentucker

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The best mod is to eliminate the aux altogether. You can replace it with a Genesis dual battery setup or you can just do away with it.

Yes. The aux will die and drain the main battery, leaving you high and dry.

Opinion
 

exfil offroad

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I was looking at the fuse descriptions on the underside of the PDC cover and saw this - F42 PCR CTRL FEED (ESS)*. Removing this fuse defeats the cold start aux battery test and allows the aux battery to be disconnected without generating any errors.

Unplugging the PCR has always been an alternative to using an N1 N2 fused jumper, both methods defeat the aux battery pass/fail test that occurs prior to a cold start. Unlike using a jumper, unplugging the PCR doesn't require any additional parts, it's just not easy to get to the PCR plug. Removing the F42 fuse accomplishes the same thing as unplugging the PCR, both actions prevent the PCR from activating and separating the batteries.

Here's the underside of the PDC cover showing the description and location of the fuse.
pcr-fuse-pdc-jpg.jpg



Here's the fuse location with the fuse removed.
pcr-fuse-pdc-2-jpg.jpg



Here's the schematic showing the fuse in the circuit.
pcr-fuse-2-jpg.jpg
Do you have the AUX buttons? If so does your vehicle not disabled those buttons when you do this?
 
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jebiruph

jebiruph

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Do you have the AUX buttons? If so does your vehicle not disabled those buttons when you do this?
I don't and it wouldn't. AUX button disabling is based on the main battery status, not the aux battery.
 


exfil offroad

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I don't and it wouldn't. AUX button disabling is based on the main battery status, not the aux battery.
actually the auxiliary battery causes the aux buttons to not be available when charging. So when that system acts up the AUX buttons are disabled.
 
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jebiruph

jebiruph

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actually the auxiliary battery causes the aux buttons to not be available when charging. So when that system acts up the AUX buttons are disabled.
It's based on the main battery status as reported by the battery sensor. The aux battery doesn't have a battery sensor, so there is no way to know if it's charging or not.
 

ShadowsPapa

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actually the auxiliary battery causes the aux buttons to not be available when charging. So when that system acts up the AUX buttons are disabled.
It's based on detected voltage -


Aux Switch Bank Module (ASBM) Battery Minimum Voltage: 11.8 V
 

ShadowsPapa

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Not being a smartass, school me here, why would I want to do this?
No real reason if things are working correct and for the vast majority, there's not going to be any issue.
But this is the internet, so things look worse and appear to happen to everyone. Neither is the case.
Mine is fine. I have no plans to disable or bypass anything.
If for some odd reason I would be one of the minority that have any issues, I'd know how to resolve it without trouble.
The problem is that all battery issues get lumped together and blamed on the same things, even though that's like saying because you have a temperature of 102 your illness is always the same.
Batteries fail for many reasons. And as I've found, a failed battery doesn't always mean disaster.
This sort of thing is mostly going to be of interest to a very few people.


Whoever came up with the aux battery idea in the first place needs to put on medication
It's not just Jeep and for the vast majority, it works fine. Only a few have issues, they just happen to be the most vocal because they are pissed off.
I resolve the issues and move on.

Again, it's the internet.

This system has been used in other vehicles for years.

 

 
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