Two of three key fobs stopped unlocking with new batteries but continue to start ignition; third fob functions normally

[mistahsnowman]

Hi all--

I have a 2019 Fiesta ST with 3 key fobs that came with the vehicle on purchase. The vehicle has ~52k miles. I now have two odd issues that came up rather suddenly.

Last week, two of the three fobs stopped working. They will start the car when held up to the ignition, but do not respond to button inputs (they will not lock or unlock the car, panic button does not work). In addition, after starting the car, I get the "key outside vehicle" error message even when the key fob is inside the car. The third fob works fine. I assumed the batteries were dead so I replaced the batteries on both malfunctioning fobs and noticed no change.

The fact that they start the vehicle tells me there is no issue with their connection to the ST. The fact that one key fob continues to work fine tells me that the proximity sensors on the vehicle are functioning normally. The new batteries aren't the culprit either - I swapped the battery from the good fob to both of the bad ones and also noticed no change.

I cannot find any threads dealing with this particular issue. Any idea what might be causing this?

 

[SteveS]

I don't know why they are malfunctioning but that might be the reason the PO had 3 keys. The car only comes with two, but if they had malfunctioning keys that might have been the reason for having a third key made.

 

[mistahsnowman]

SteveS - I would agree that your thoughts make sense except we bought the car over 3 years ago. I probably should have mentioned that in the original post. Tough to know how much detail to include. The previous owner only had the ST for an 18-month lease, and I got a third fob thrown in from the dealer when we bought the car (that third fob is one of the ones that is dead now).

 

[ghodge]

Batteries these days have a bitter tasting coating on them that sometimes prevent reliable contact depending on where the contact is made on the battery. I ran into this problem with both my remotes and Apple air tags. I think I had to mildly rub or sand the surfaces before I could make good contact.

 

[LilPartyBox]

^ you may have a point. I just changed the battery on mine 2 days ago and I’m still getting intermittent battery warnings about the fob. Maybe it’s that coating randomly futzing with conductivity

 

[mistahsnowman]

Thanks for everyone's comments.

I figured out that the problem was probably poor quality control with the batteries, not the fobs, so now I feel a little stupid. I got a brand new package of Duracell 2032's and all three fobs now work.

The older batteries read 3V +/- a little, so I measured them with calipers, and they were ever so slightly thinner than the Duracells. I cleaned up the contacts, de-compressed the contacts a little, and put them in. Lo and behold, all three fobs now work. I'm not exactly sure why one of the old batteries worked in one fob but I expect that the contacts were a little less compressed than in the other fobs so the battery height didn't make a difference. Surprised that was the issue but oh well. That was a lot of unnecessary hassle on my part haha. Thanks again for everybody's thoughts.

 

[XR650R]

Glad you got it solved.