AUX battery delete/bypass - Which method is proper?

[Opus]

So... I just finished the battery bypass.

Removing F42... easy-peasy

Disconnecting the auxiliary battery negative terminal from the main.... easy right up to the point where I separated the terminal from other negative terminal and got sparks between the two. I knew not to let either negative cable get anywhere near the positive terminal on the battery, but I wasn't expecting an arc between the two negatives. That scared the shit out of me thinking I had somehow just fried the electrical system.

Got the auxiliary battery negative terminal end swaddled in electrical tape and zip tied to keep it from bouncing around., reinstalled the other cable on the 10mm post on the main battery and the Jeep started just fine.

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[Guale93]

I removed the auxiliary battery from my JL 2.2, and I must say it was quick and easy from the wheel well.
I isolated the positive and negative wires inside the AUX battery box. Should I also disconnect and isolate the negative wire leading to the main battery?
I also removed fuse 42, although it probably wouldn't have been necessary since I'd already deactivated the S&S via JScan.

 

[ScotM]

Just a note. I typically get a small spark when disconnecting or reconnecting my negative terminal. And I am pretty sure that disabling start stop in JScsn will not actually disable the start stop unless one of the hood latches is disconnected - there is some process JScsn outlines in addition to disabling via their app.

 

[THAW]

I isolated the positive and negative wires inside the AUX battery box. Should I also disconnect and isolate the negative wire leading to the main battery?

Completely unnecessary, but won't hurt anything.

I also removed fuse 42, although it probably wouldn't have been necessary since I'd already deactivated the S&S via JScan.

In a counterintuitive way, that's correct. Disabling ESS with JScan triggers the @! dash light; disconnecting the AUX (ESS) battery without removing fuse F42 also triggers the @! dash light (for a different reason).

That is, because your JL isn't an early '18, it'll start with the AUX (ESS) battery disconnected and fuse F42 in place, so given the dash light is already on, leaving the fuse in the PDC would make no outward difference. It would cause the PCM to silently reset due to abrupt power loss at every cold start, though - which may ior may not shorten its service life.

[All assuming Euro-spec JLs behave identically with respect to the involved systems.]

 

[Guale93]

On my late 2019 model, I've never had the ESS light on the dashboard, neither when I disabled it with JScan nor now that I've removed AUX and F42. Probably, as you say, the European ones are different.

 

[THAW]

On my late 2019 model, I've never had the ESS light on the dashboard, neither when I disabled it with JScan nor now that I've removed AUX and F42. Probably, as you say, the European ones are different.

Did you remove one of the hood switches from it's bracket so it can stay in the open position, as instructed by the JScan docs? That's what actually disables ESS in the PCM and causes the @! dash light; JScan just prevents the BCM from tripping a bunch of warnings due to the open switch by setting its "hood sensor present" to inactive.

If you changed the ESS settings in JScan without the hardware change, ESS is disabled for some other reason (e.g. IBS SOC below 65%). [Or, possibly, Euro differences.]

 

[Guale93]

Did you remove one of the hood switches from it's bracket so it can stay in the open position, as instructed by the JScan docs? That's what actually disables ESS in the PCM and causes the @! dash light; JScan just prevents the BCM from tripping a bunch of warnings due to the open switch by setting its "hood sensor present" to inactive.

If you changed the ESS settings in JScan without the hardware change, ESS is disabled for some other reason (e.g. IBS SOC below 65%). [Or, possibly, Euro differences.]

I'm absolutely sure that 3 years ago, when I turned off the ESS, everything worked perfectly (including the charged battery). It probably depends on the differences between Europe and the US.

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