Key Fob Confusion

[Asim]

Hi Guys (and gals)
Just picked up a 17 GT350 from a dealer many miles away. Car is amazing, with the one exception of the key fobs not working...usually. Which is the confusing part. They both seem to work (lock and unlock the car) when it is warm and I've come back from a drive, but neither work when the car is cold, even if I am sitting in the car. Putting either in the cup holder does work also. I've tried the programming several times and never get the flashers to accept, but as I say, they do work "sometimes" which tells me it's not the programing, and it's not the batteries, so what the heck is it? I also fully charged the main battery overnight just in case and no dice.

Thanks in advance,

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[Asim]

Still hunting around trying to solve this. Changed both fob batteries twice and tested each battery at 3.3v. Works when in the cup holder so its not programming (correct). Also btw, works when the car is warmed up, but not when it is just stilling in the garage. Anyone else have this type of intermittent problem?

 

[Torched10]

Still hunting around trying to solve this. Changed both fob batteries twice and tested each battery at 3.3v. Works when in the cup holder so its not programming (correct). Also btw, works when the car is warmed up, but not when it is just stilling in the garage. Anyone else have this type of intermittent problem?

For what it's worth that happens to me when car isn't driven fir couple weeks. Might check ford pass
There have been several posts on here about resetting the battery monitoring system so the car knows the battery is OK.

 

[Goterr0r]

I believe the fob antenna is in the center console. Make sure you don't have anything in there that could be jamming the signal a bit. If that's where you store you tin foil hat, it could be the issue... lol

The antenna itself could also just becoming weak or something as well.

 

[ORRadtech]

I believe the fob antenna is in the center console. Make sure you don't have anything in there that could be jamming the signal a bit. If that's where you store you tin foil hat, it could be the issue... lol

The antenna itself could also just becoming weak or something as well.

I was thinking an antenna issue as well. Or possibly a problem with the module. Or even a ground issue. A wire could have a microscopic crack or a corroded connection and have the symptoms the OP describes. If the module or antenna is under the console it's entirely possible something was spilled and is now causing problems.
I definitely don't think it has anything to do with the fob and/or the car batteries.

 

[Tucker80]

How are you starting the car after parking overnight if neither fob works when the car is cold?

 

[ORRadtech]

How are you starting the car after parking overnight if neither fob works when the car is cold?

The fob doesn't have to work if you insert it into the slot in the cup holder. It will start the car even if it's completely dead. Just leave it unlocked to get in. Or use the physical key to unlock the door.

 

[Skye]

There are a series of cables which run down the spine of the transmission tunnel. Could be something has wiggled loose over time, rubbed and broken or simply failed.

That it works when hot is promising; that partially loosened or broken connection has expanded enough to pass a signal to the Body Control Module.

My initial thought is to start at the console and remove it, slowly, checking each connection and contact from the dash to the rear seat area.

If you think you have found something and fixed it, leave everything discombobulated, then try the fob when car is stone cold.

 

[Asim]

Some progress - Even though I fully charged the battery overnight and it read 13.2v. Even though I connected my wife's QX60 battery while running, and got 14.5 to the Shelby battery. Even though both those didn't work. I disconnected the Shelby battery and installed the one from the QX60, and it worked right away. Looks like the car battery is the culprit. I will update this thread if it stops again and I find something else for the next victim.
Thank you all for your support. Love the Mustang community.

 

[Torched10]

Some progress - Even though I fully charged the battery overnight and it read 13.2v. Even though I connected my wife's QX60 battery while running, and got 14.5 to the Shelby battery. Even though both those didn't work. I disconnected the Shelby battery and installed the one from the QX60, and it worked right away. Looks like the car battery is the culprit. I will update this thread if it stops again and I find something else for the next victim.
Thank you all for your support. Love the Mustang community.

Your testing alternator out put
To measure battery voltage the car shouldn't be runnimg
Battery voltage dhoukd be 12v to 12.6
Use a digital volt meyltrr and just measure the battery voltage at the battery's

 

[Asim]

@Torched10 I did do that initially (car off) and the battery was 11.7 cold. Charged over night and got it up to 13.2. But still didn't help the fobs. Disconnected and connected my wife's battery (also 13.2 ironically) and they work. Does that help?

 

[ORRadtech]

I'm going to be very surprised if the car battery is the problem. Not saying that a weak battery doesn't cause odd issues because they certainly do. But this isn't one that is reported very often.
Also, 13.2V is probably what is known as a surface charge. That's kind of a false reading that usually happens immediately after charging. The best way to check a battery's health is a load test. Most auto parts stores will load test them for free. I will attach a chart that will give you a rough idea of a lead/acid battery's state of charge. Be sure to measure voltage after removing the surface charge.

 

[Asim]

Anybody know where the remote antenna is located? Not programing as it works in the cup holder. Changed (and tested) both fob batteries and changed main car battery and no dice.

 

[Mike Pfeifer]

Anybody know where the remote antenna is located? Not programing as it works in the cup holder. Changed (and tested) both fob batteries and changed main car battery and no dice.

Did you do the BMS reset after battery replacement?

 

[Asim]

Thanks for the suggestion. Reset complete, but no luck on the key not detected. I'm going to try fuse in the pass kick panel next.

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