FOB Problem??

[cadyshac]

Looking for a little help here. I have a '18 JL Sahara Unlimited owned it since new. Recently got a message a few times saying auxiliary battery low when the engine would restart at a stop sign or light. Then last week during a stretch of cold weather the fob would not unlock the doors. I used the key to unlock the door and that set the alarm off. Starting the Jeep from the dash turned the alarm off and all operated normally. Yesterday I replaced the auxiliary battery but the fob unlock feature is still not working. All the other fob functions work just fine, only the unlock doesn't work. Does this seem like a fob problem unrelated to the auxiliary battery? Also I only have the 1 fob, the other was lost a couple years ago. I have not had a chance to drive the Jeep yet since the new battery install, I'm hoping charge the new battery or reset something in the system?
Thanks in advance for any tips or advice.

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[oldcjguy]

Usually a good idea to replace both batteries at once. Aux and primary together. They are wired together and one will bring the other down. A 2018 battery is probably near end of life anyway.

As for the fob... Have you changed the battery in the fob? If so and if the other push button functions work, like horn and lock, I'd guess it's a fob problem.

 

[cadyshac]

Did not change fob battery yet. Had a dealer "test" the fob and he said all is ok, I guess I don't trust him because there is still a problem.

 

[cripton805]

I second that the main battery is probably toast. If you don't replace it and it can't hold a good charge. It will also kill the new aux battery and drain that.

Might as well change the FOB battery too. Can't hurt. ??‍

 

[cadyshac]

Everything work’s fine except the unlock button on the fob
No one thinks this is a fox problem?
It has never struggled to crank or start or any other sign of a weak battery

 

[oldcjguy]

Everything work’s fine except the unlock button on the fob
No one thinks this is a fox problem?
It has never struggled to crank or start or any other sign of a weak battery

I think it's probably a fob problem, but I'd take it apart, change the battery and clean it if there's corrosion.

One othert thing, do the power locks work to unlock the jeep from the inside when it's locked? (Using the button on the doors)

 

[kkarnage]

You said “cold weather” and “fob”. I’d wager good money on it being the fob battery. I’ve had this multiple times before with JL fobs: the unlock (and proximity unlock if you have that) seems to be particularly sensitive to battery voltage, and in cold weather that fob and battery get a LOT colder than you might imagine.

I’ve managed to sort it out temporarily by putting the fob somewhere warm, like my armpit, which sorts it out pretty quickly (matter of minutes).

But yeah, change that fob battery. Pro tip, don’t use Duracell brand batteries as replacements. They have a coating designed to allegedly prevent kids putting them in their mouths which messes with the fob contacts. Grab some energizer batteries instead. In a pinch you can run some fine grit sandpaper over the Duracell battery to get the coating off, but personally I’d get Energizer.

 

[cripton805]

I'm only recommending the main battery replacement because you had to replace the aux battery. Which means the main battery is also probably on the way out too.

It will toast your new aux battery and have to replace it a second time.

But, do you have the second FOB? Why don't you use that one and test it?

 

[cadyshac]

I don't have the 2nd fob.
Went from bad to worse today. Jeep now won't recognize the fob and I've tried 2 new batteries in it. The car will remote start just fine off the fob, it will lock the doors too but it will not unlock. And now it wont start from the pushbutton, even if you push the button with the fob. Going to dealer in the morning and hope he can find a problem with the fob. The led on the fob lights when you press the lock button but it does not light up when you press the unlock button. I had to pull the horn fuse, it was driving us crazy every time you had to unlock the door with the physical key. We do not have the keyless touch entry, just the fob that's not working.
Could this be a bad module on the jeep itself?

 

[REWJeep]

You might consider buying another one or more keys when you are at the dealer. (I'm a belt and suspenders kind of guy and bought two extras for my Wrangler. One for my pocket; one for my briefcase or backpack; one for my wife's purse and one in the safe. I would be quite anxious if I had only a single key.)

My dealer's parts department obtained the FCA(?) authorization and cut the keys within an hour on a Saturday morning. The service department then had them programmed to my Jeep in another hour. The total cost was about $360 each.

I sure wish that Jeep had a valet key and a wallet key along with a fob like my Audi did instead of only the giant fobs.

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