I have a 2023 Chrysler 300 and it recently complained that my key fob's battery was low. I replaced it with a new one (several times with new, measured good, batteries) but the fob stopped working for my car. The original battery measured 3.00 volts, hardly "bad" for a CR2032.

I have attached a picture of what my fob looks like since there seem to be many variations of fobs.

I have looked in many places on the Internet and none of the instructions are for my car and fob combination to reprogram it. They all say to insert the emergency key from the fob in the ignition. My car has no mechanical ignition, just the start button.

I can still open the door with the emergency key and I can start the car by pressing the fob on the ignition start button but I cannot find any instructions for reprogramming the fob to work in proximity.

I have a second fob and it still works but even it stopped working after I changed the battery. I re-seated that battery and it started to work again. No such luck with the other fob that I'm writing about here.

I also noticed an odd, I guess conductive, goo on the terminals for both positive and negative from the factory. This got mostly wiped off and discarded with the original battery. What is that stuff?

The new, replacement batteries are "Sony" and measure 3.3 volts.

Please provide specific pointer to instructions for my setup if you can. Remember, there is no ignition hole for the emergency key. I looked in the glove box and the console. If I missed it, please provide a picture of where it is?

I also saw some reference to later model 300 vehicles that use an app from Stellantis. Do I need to use that app in UConnect? If so, how does that work?

 

The batteries that I ordered came yesterday.

The car is in the garage which is at least 60 feet and four walls away from my office. I took the Sony battery out which measured 3.3 volts a few days ago and it measured 3.12 volts now. I measured the new Panasonic batteries which just arrived and they measured 3.23 volts but they obviously work better under this load.

I pressed all the buttons on my fob from this distance and with those obstructions in the way and they all worked. The panic horn came on and I could even turn it off from my office.

I went to the garage and the trunk was open and the doors were locked since that was the last of the lock or unlock buttons I pressed from my office. I had my fob with me and the door unlocked when I grabbed the door handle. Finally, the car started when I got in the car with my fob. Basically, everything worked.

I removed the Sony battery from my wife's fob and replaced it with one of the new Panasonic batteries and everything tested out the same as my fob did, even the unlock, lock and panic on, panic off and trunk open, from my office.

Bottom line, the new Sony batteries measured good (even higher than the new Panasonic batteries) but they were no good under load after several years on my shelf.

For what it's worth, the new Panasonic batteries are labeled "Keep out of the Reach of Children" and say nothing about being coated with anything. The Amazon site says "Child resistant packaging" but nothing about coatings, if that makes a difference to anyone. They have a shelf life date of December 2031.
Problem solved . [img alt=""]data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7[/img]

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Here's an interesting site...

https://www.bettlink.com/blog/cr2032-battery-ultimate-guide-2025

 

When you see "goo" on new or old batteries it's a sign the battery is bad. No question about it.

 

Well, not this time. Turns out the "goo" was added by Chrysler or the local dealer for better conduction and to stop corrosion.

 

And I thought I was sooooo smart.