Glow Plugs: which battery?

[G-Oil Guy]

I’ve been trying to find out which battery provides power to the glowplugs with no luck.

does anyone here know?

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[BDinTX]

That would be the big battery. The smaller one is only supposed to power electronics during an ESS event.

If you’re still getting that check engine light at start for glow plug voltage, disconnect the negative cable for the auxiliary battery where it ties into the big battery. Wrap it well with electrical tape, then disconnect fuse 42. That will eliminate the auxiliary battery from the equation.

 

[Deleted User 38384]

That would be the big battery. The smaller one is only supposed to power electronics during an ESS event.

If you’re still getting that check engine light at start for glow plug voltage, disconnect the positive cable for the auxiliary battery where it ties into the big battery. Wrap it well with electrical tape, then disconnect fuse 42. That will eliminate the auxiliary battery from the equation.

I learn something new everyday!!

I’ve been trying to find out which battery provides power to the glowplugs with no luck.

does anyone here know?

How old is your battery?

My factory battery only lasted about 2 years.

If you buy an new 94r battery for your ecodiesel, but I recommend one with 850 CCA.

I went with optima this last time, but I've had a so-so experience with it so far. I'll probably go with the crowd favorite Odyssey next go round.

Really interesting topic, appreciate y'all's info and time!!

 

[AndySpill]

I don't know squat about the Diesel JL.

But unless it is different than the dual AGM battery gasoline version, when circuit 42 is not energized, both batteries are in parallel, both running appliances and both getting charged.

The smaller battery **pretty much only powers electronics during an ESS event, but during non ESS events it works with the main battery to power electronics as well.

** I think @Jebiruph did some research a while back and found that some things during ESS events, like power steering, are powered by the main battery. Perhaps this is why an ESS event won't engage if the steering wheel is turned too far in either direction.

Maybe the Diesel JL does uniquely tap the main battery for the glow plug but I would be surprised to find this to be the case. The glow plug would seem to have to connect directly to the main battery AND circuit 42 energized for separation of the batteries to take place--unless Stellantis wires the diesel batteries differently.

 

[SonofaSeabee]

That would be the big battery. The smaller one is only supposed to power electronics during an ESS event.

If you’re still getting that check engine light at start for glow plug voltage, disconnect the positive cable for the auxiliary battery where it ties into the big battery. Wrap it well with electrical tape, then disconnect fuse 42. That will eliminate the auxiliary battery from the equation.

Positive cable? Never heard of this. Negative cable, yes, heard of this.

 

[jludave]

disconnect the positive cable for the auxiliary battery

No. You want the negative cable.

 

[BDinTX]

Crap my bad. Negative cable.
Going from memory… no bueno.

 

[G-Oil Guy]

Thank you all for the info.

@BDinTX yep. Still getting the light with the blinking glow plug and this is after fully charging the batteries and then disconnecting them to clear the light. Came back on within a few power cycles.

At this point I think it’s either the battery (original battery from 2021) or the glow plug relay or the control module.

 

[BDinTX]

I still think it’s worth separating the auxiliary battery even if only temporarily. The small ones tend to go bad first then drain the life out of the big one.

Plus it’s basically free to try.

Did you check their voltage with a meter when you had them out?

 

[G-Oil Guy]

I didn’t but I can how do you check the small battery? I’ve only ever seen the one positive terminal

 

[BDinTX]

Sorry I thought I read that you had the batteries out. There’s a great diagram at this link.
https://www.jlwranglerforums.com/forum/threads/ess-dual-battery-management.60034/

It looks like the aux connects to N1 on the high current fuse array. Be careful when messing with it, a replacement is about $60.

Personally I think I’d disconnect the cables off the main battery and test it across the battery posts. Then test the aux from the disconnected battery cables since they’ll still be live from the auxiliary battery.

I’m just some random on the internet so use your own judgement.

 

[Wrangler man]

The aux battery is the catalyst to many many problems. The stories of those problems and now this one never end. The stop start was just a carryover from the gassers. Never should have been put on the diesel platform. Along with many other emissions components that harm, and shorten the diesels life, often with VERY expensive repairs. Resulting in replacing components at the consumers expense. If it wasn't for big brother putting the pressure on automakers to squeez out every micron of emission, the start stop never would have been implemented. The start/stop is a engineering failure and Stalantis knows it but refuses to recognize it and fix it. So we the consumer are left to do the best we can with this NEVERENDING dilemma. IMO pull it, eliminate it COMPLETELY. Don't pull fuses, just the aux battery. To date my many tows to the dealership and array of dash lights have all ended since eliminating the cause, the AUX BATTERY. GOOD LUCK.

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