2018 Key fob not working overnight

[KenK]

2018 XLT Max, 50k miles, never been to the dealer (thankfully)
Both key fobs are not working after the truck sits overnight.
They work fine all day, but after sitting overnight I have to unlock using the door pad or the key in the door.

I tested the original vehicle battery and it was right at 12 volts.
The auto start/stop seldom worked (probably due to low voltage) but the truck always started instantly.
I changed the vehicle battery being sure to maintain 12v to the cables at all times so not to lose memory or other settings.

After changing the vehicle battery the start/stop works all the time now, which is annoying.
However, the issue with the key fobs is the same. After sitting overnight, neither of them unlocks the doors normally.
One of the key fobs is used daily and the other is rarely used and kept in a drawer.
I tested the batteries in the fobs but have not replaced them yet since they tested strong.
Sometimes if I stand next to the door and keep pressing random buttons it will unlock, most of time I have to use the key pad on the door or the door key.

Any ideas? I searched the forum but did not see anything quite like it, that or I am just a bad searcher.

Ken K

 

[BigOleFordFan]

Sometimes if I stand next to the door and keep pressing random buttons it will unlock

This would seem to indicate an issue either with the fob batteries, the fob itself, or the receiver in the truck.

Just curious, does this only happen at home, or anywhere after it sits for a while ? And how do you lock the truck, and is that also an issue, even sometimes ? If it only happens @home, then perhaps there is a strong source of signal interference somewhere close by that is causing it to happen.....

If the truck starts normally after unlocking, I would start with changing the fob batteries, then the fobs, then the internals, which probably means a trip to the dealer, unless you have the proper tools & equipment to diagnose/fix it yourself

 

[KenK]

Thanks for the reply. The fob batteries tested ok but I ordered some new ones from amazon which should arrive tomorrow. I will let you all know if there is any change.

 

[Woodwolf]

This would seem to indicate an issue either with the fob batteries, the fob itself, or the receiver in the truck.

Just curious, does this only happen at home, or anywhere after it sits for a while ? And how do you lock the truck, and is that also an issue, even sometimes ? If it only happens @home, then perhaps there is a strong source of signal interference somewhere close by that is causing it to happen.....

If the truck starts normally after unlocking, I would start with changing the fob batteries, then the fobs, then the internals, which probably means a trip to the dealer, unless you have the proper tools & equipment to diagnose/fix it yourself

I would probably rule out the receiver too, otherwise truck wouldn't start. Unusual is that both Key fobs apparently fail at the door but still start the truck. HMMMM

 

[JamaicaJoe]

Devices like key fob's operate on radio frequencies in the ISM band. Basically that is a catch all for all sorts of devices that operate on a basis that they may interfere with each other. I bought some remote digital thermometers for my refrigerators and freezers. I bought two different models fro two different vendors. Guess what, at times they either interfere with each other and jam or display temperature from the wrong fridge. Turns out that the devices use same ISM freq and coding scheme. At times another thermometer that I se for outside temperature jams everything because it gets stuck on transmit due to a weak battery. You may be getting interference from something locally. It could be another key fob for a different vehicle, a garage door opener or even military and federal government radios which operate adjacent to these ISM bands. If you can move the vehicle to another location, try and see if the Fob works reliably. Then look around for any other devices that you have added, or suddenly don't work either.

 

[KenK]

Dooh, I replaced the batteries in both fobs and they worked fine yesterday and today.
Just because the battery tester said the fob batts were good they did not have enough oomph.
I feel kind of dumb posting this but I owed ya'll an update.