Keyless entry stopped working

[Viking84]

They are correlated, but charging system voltage does not reflect battery voltage.

Aha, that's where I went wrong, I just looked at the voltage the car displayed once I turned the engine off. Was higher than expected. I'll use a voltmeter and check this morning as the truck has been cold all night

I have a battery tender that I usually use for my ATV and motorbike, anything to worry about using something like this on the Raptor? We're probably going in to lockdown (or at least home office work) here due to Omicron so the Raptor might be used very little for a month or so.

 

[FordTechOne]

Aha, that's where I went wrong, I just looked at the voltage the car displayed once I turned the engine off. Was higher than expected. I'll use a voltmeter and check this morning as the truck has been cold all night

I have a battery tender that I usually use for my ATV and motorbike, anything to worry about using something like this on the Raptor? We're probably going in to lockdown (or at least home office work) here due to Omicron so the Raptor might be used very little for a month or so.

As long as the charger is automatic and compatible with AGM batteries, it should be fine.

 

[TexasAggie94]

Check your battery. When it gets drained those functions and others stop working. Just went through this. Get a battery tender to keep it topped off.

Do you know if the passive key function being shut down would affect just one side or not? My passenger side passive entry just stopped working recently out of the blue but the driver side still works normally. I did see in the manual that they are separate in the fuse box.

 

[smurfslayer]

I believe it starts with the passenger side. you can use the auto stop start menu as a guide. if you take off and get the truck warm and AS/S is disabled for charging, drive around for a while and it may be ok once charged.

 

[GordoJay]

It's hard to imagine keyless entry using enough power to require shutting it down whenever the battery gets a little low. It must be sitting there transmitting like a MFer all the time.

 

[isis]

It's hard to imagine keyless entry using enough power to require shutting it down whenever the battery gets a little low. It must be sitting there transmitting like a MFer all the time.

It’s not the biggest draw, it’s the easiest and least impactful thing to shut down.

 

[TexasAggie94]

It’s not the voltage that’s the issue, it’s the state of charge. The truck monitors the amperage being drawn from the battery; once it becomes too low on charge, it starts to shut off various features. For some reason one of them is the passenger side passive entry door handle.

As the truck is driven and the battery state of charge increases, the passive entry should start to function again. Alternatively, you could charge the battery with an AGM compatible charger and then perform a Battery Monitoring System Reset using ForScan.

@FordTechOne sir, wanted to confirm that the passenger side door keyless entry door handle can go dormant in a low voltage situation while the driver's side handle will still be operational? I would like to confirm this before I take my truck in and they start ripping off the door panel. Do you know what voltage/amperage I am looking for at the battery terminals to determine if this could be the cause of that module being shut down? Thanks in advance.

 

[MRV99]

It's hard to imagine keyless entry using enough power to require shutting it down whenever the battery gets a little low. It must be sitting there transmitting like a MFer all the time.

It is still a system which has to constantly monitor an antenna for the presence of a “signal” which allows the system to unlock. It also has to decipher if the signal is in the right area to unlock or start the car.

 

[GordoJay]

It is still a system which has to constantly monitor an antenna for the presence of a “signal” which allows the system to unlock. It also has to decipher if the signal is in the right area to unlock or start the car.

Receivers need very little current, they're just a chain of log amps. Transmitting takes a lot. I suspect that the fobs mostly receive because the battery is small. An automotive battery is huge, though, and I'd expect it to be able to power a transmitter for months

 

[FordTechOne]

@FordTechOne sir, wanted to confirm that the passenger side door keyless entry door handle can go dormant in a low voltage situation while the driver's side handle will still be operational? I would like to confirm this before I take my truck in and they start ripping off the door panel. Do you know what voltage/amperage I am looking for at the battery terminals to determine if this could be the cause of that module being shut down? Thanks in advance.

Correct. For some reason the passenger side is the one that stops functioning when battery voltage drops.

Even if the battery is fully recharged, a battery monitoring system reset will often need to be performed so the BCM knows the battery is no longer discharged.