N1 N2 bypass

[Fitzz47]

Do you need to undo the Aux neg
Terminal. After jumping n1 to n2?
Or can you just jump n1 to n2 and not
Disconnect the neg. terminal.

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[sourdough]

I have the jumper with a 40 amp inline fuse that I leave out. Only will resort to installing it if I have an issue. my rig is not a DD'r and sets for more than a week at at time. I keep plugged in a 1.5 amp solar battery maintainer. I've never had a battery issue in my 2 year old JLR.

 

[Fitzz47]

I have the jumper with a 40 amp inline fuse that I leave out. Only will resort to installing it if I have an issue. my rig is not a DD'r and sets for more than a week at at time. I keep plugged in a 1.5 amp solar battery maintainer. I've never had a battery issue in my 2 year old JLR.

Do you have the aux battery disconnected.

 

[Fitzz47]

I just want to be able to start my 2018
If the aux battery fails. I can wire n1 to n2. And pull the fuse. Can I keep the aux
Battery connected

 

[Rhinebeck01]

@Fitzz47

You have a 2018 JL.... You do not need to use an N1-N2 fused bypass jumper, if your Aux dies, so you can start with a good Main, as long as you have had TSB 18-092-19 applied to your 2018 JL.

FCA has an update.... It is TSB 18-092-19. Since you own a 2018 JL, you will definitely want this update!

Along with fixing the hi rev issue, TSB 18-092-19, addresses how the JL deals with a depleted Aux battery. Without this pcm update, if the 2018's, Aux battery is depleted, the 2018, JL will not try to start.

With this pcm update, the 2018 JL , with a depleted Aux battery, will try to start, will fail, but will start on the 2nd attempt, so you are not left stranded / no start scenario.

2019 and newer JL's left the factory with this pcm update.

Again if you have a 2018 JL and it has not had this update, do get it done.

IF, your JL has over 36,000 miles and your regular warranty is finished, the dealer can do this update on your JL for free as the update is covered under the longer power train warranty..

Read here, BEFORE you go to dealer asking for the update:
https://www.jlwranglerforums.com/forum/threads/my-dealer-won’t-flash-my-2018-wrangler-pcm.66199/post-1401777

 

[sourdough]

No n1-n2 needed on my '19 JLR. excellent news

 

[melendez69]

I just want to be able to start my 2018
If the aux battery fails. I can wire n1 to n2. And pull the fuse. Can I keep the aux
Battery connected

See post #326 here. There's a wealth of information there and also here.

 

[WranglerMan]

If you have a 2018 have the dealer apply the TSB that addresses the issue if the aux fails you can still start, if you want to bypass the aux jumper N1 to N2 and remove the ESS negative off the main but don’t use ESS as it will tax the main crank battery and if you want to get rid of the crappy FCA design their are other more costly options just depends on your needs.

 

[Gee-pah]

Do you need to undo the Aux neg
Terminal. After jumping n1 to n2?
Or can you just jump n1 to n2 and not
Disconnect the neg. terminal.

OK Jim...here's the skinny.

The fused jumper from N1 to N2, while an excellent all time best device from forum user @Jebiruph Jerry, has somewhat, as a result of changes FCA has made to the vehicle, been rendered obsolete in its original purpose. Jerry has built upon it though in ways that have made its use in more extensive hacks worth considering.

Examining only the N1 to N2 hack:

In 2018, 3.6LJL's would be stranded if their ESS/Aux battery lacked sufficient charge when a crank was attempted. In 2019, FCA changed the logic such that if this ESS/Aux battery was bad, subsequent crank attempts would be solely off the main battery. If successful, the vehicle would disable ESS, and keep it off until the ESS/Aux battery's issues were addressed, and a crank was thereafter attempted.

I think the rig, on the second attempt to crank, effectively does Jerry's hack all on its own!!!

If the ESS/Aux battery test is passed, both batteries are reconnected in parallel and both power the crank. It's why in 2018 and 3.6 JL could cold crank and run solely off a (charged) ESS/Aux battery, but not solely off a main one (because the ESS/Aux battery test would fail.)

2018 3.6 JL owners with TSB 18-092-19 will have their vehicles behave at crank like the 2019 model year and after 3.6 JLs.

It made no difference how much power the main battery had in these 2018 3.6 JLs. A dead ESS/Aux battery without Jerry's hack meant a vehicle that was not capable of starting.

Jerry's hack made a hard wired connection from N1 to N2 such that any calls to access the ESS/Aux battery (via N1) will ALSO be routed to the main battery (N2) vis a vis this connection. It allowed 2018 3.6JLs without this TSB I referenced, and with bad ESS/Aux batteries, but adequate main batteries, to still crank.

Let's look at what happens though based upon whether or not you disconnect the cable that connects the negative posts of both batteries. If disconnected, your 3.6JL becomes a one (main) battery vehicle. Never is the ESS/Aux battery tapped for current nor charged. Any calls by the vehicle to the ESS/Aux battery get rerouted to the main battery.

Keep this cable connected and upon successful crank of the vehicle the alternator will attempt to charge both batteries. Calls to the ESS/Aux battery in this setup get routed to both batteries.

There are more implications. That N1-N2 fused wire is 99% of the time redundant. 99% of the time N1 is connected to N2 by the vehicle itself including when parked. In fact the only time the two terminals are not connected is for that instant at startup when the ESS/Aux battery is tested in isolation, and during ESS events . The fused jumper just changes the two terminal's connection to 100% of the time: even at cranks and even during ESS events.

One of the implications of this connection of the cable that connects both batteries' negative terminals is that during rest the two batteries are connected in parallel and a bad battery might drain a good one. Disconnecting the cable that connects both batteries negatives will make any draining of the main battery while at rest, to attempt to charge a weaker ESS/Aux battery impossible, and I might point out, vice versa.

With this N1 to N2 hack in place, whether you've committed to taking the ESS/Aux battery out of the picture by disconnecting the two battery's negative terminal's cable or not, I recommend disabling ESS.

I say this because by factory wiring, the ESS battery alone runs ESS events, and if it gets too low in voltage, the parallel connection between the two batteries is reestablished and both batteries combine their power to recrank the engine to get the alternator back in the business of charging both batteries. With the N1-N2 connection ESS events will be taxing the same main battery normally isolated by the factory design to save its power for the recrank. The only difference is that if you keep the cable between the two batteries' negative terminal connected, both batteries run the ESS event, and if you disconnect this cable only the main battery runs the ESS event.

What could happen is that the tricking the rig into thinking the ESS battery is running the ESS event, as happens with the N1 to N2 fused jumper, when in fact it's the main battery (as well if the negative cable between the batteries remains)--or in isolation (if this cable is disconected,) voltage drops that inspire the 3.6L to recrank and end the ESS event prematurely (before the operator takes their foot off the brake) then tap the very voltage depleted main battery that inspired the need for the prematurely ending of the ESS event.

Sure, many vehicles run ESS systems on one battery. Perhaps my scenario will never come to pass in a one battery 3.6L JL. But perhaps the designed thresholds for ending an ESS event are more stringent in 1 battery vehicles, as opposed to the 3.6L JL.

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