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Keyless ignition, backup key blade & alt. starting/lock procedures if key fob is dead

367K views 43 replies 22 participants last post by  zulujams  
#1 ·
Keyless ignition, backup key blade & alt. starting/lock procedures if key fob is dead

Since there were a few recent threads about the keyless ignition, the backup physical key blade in the key fob, and what happens when the battery in the key fob dies I went out earlier tonight to take some pictures and put them in one thread.

First, if the battery in the key fob dies and or the car's battery is dead and you can't use the remote keyless entry to get into the car due to no power for the door locks there should be a physical (mechanical) backup key blade located in the back side of all the Intelligent Access Keys (i.e. key fob). To release the back cover on the key fob to access this backup key you pinch/depress the small ridged tabs on both sides near the bottom of the key fob just above where the key ring attaches while at the same time lifting up on the back "Ford" cover.

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NOTE: If you refer to these procedures in owner's manual it is shown under the Intelligent Access Key "Type 1" procedures.



You can then lift out the key blade and use it to open the only physical lock cylinder on the car's exterior which is located on the driver's door handle. If for some reason the car's battery were dead you would use the backup key to lock the driver's door. For the other doors, as shown below, right above the latch assembly is a small slot that you can use the key blade to turn in order to lock the other doors (which don't have a lock cylinder on the door handle).

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If the car's battery is good but the key fob battery goes dead or is otherwise damaged, the Focus models with keyless ignition do not have a physical backup lock cylinder and ignition switch located on the steering column. If the key fob's battery is dead and isn't actively able to transmit and talk to the security module in the car there is a backup, passive chip inside the key fob, likely an RFID (radio frequency identification) chip that you can hold up against the cover on the steering column.

A transmitter in the column provides power to the RFID type chip using an inductive coupling but the chip has to be very close to that transmitter in order to receive enough power for the vehicle to be able to talk to it. If you still have problems getting the vehicle to start it appears there is a slot behind the cover with tabs to hold the key fob in place and should be the optimal location for the anti-theft transmitter to be able to power and read the passive security chip in the key fob.

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Some people might be concerned that there is no physical lock cylinder/switch assembly behind the cover that could be used with the backup key blade. This really isn't much of an issue, as the ignition switch in most new cars with a conventional key doesn't act on the engine's starter directly. Instead all it does is tell the vehicle's computer that you'd like to crank the engine and the computer then in turn activates the starter relay.

Even with a conventional key, if the built-in anti-theft chip on most new car keys (or key fob on keyless systems) is broken, the anti-theft transmitter/receiver module is defective, the vehicle's computer is inoperative or there is another electrical issue, the car won't start no matter if it has a conventional key or a keyless system. By omitting a physical backup switch it likely allowed Ford to offer the keyless system at a lower price point.
 
#6 ·
It's probably not something most people will need for a few years until the stock batteries start to die (car and key fob), but good info to file away for any "just in case" problems that might crop up for those who haven't been able to study the owner's manual. Electronics are great when they work and are getting more and more reliable but it's nice to have some backup options.
 
#7 ·
Actually - I had a situation where the car would not start. I pushed the start button and I got a message that FOB was not recognized. The car would not start till I held the FOB next to the plastic door. Only happened the one time - but thankfully I was aware of the backup RFID built into the FOB.
 
#8 ·
The only thing I've noticed on my car is that if I open the car and sit on the outer part of the passenger seat and reach over to press the power/start button (such as to close the sunroof or crack open a window) it won't always work when the key fob is in my right, outboard pocket furthest away from the driver's seat area. The owner's manual mentions interference from other devices may cause an issue but I've never seen anything on the frequency range the Intelligent Access Keys work on. Unless you're doing spectrum analysis and have some high-end test gear it could be difficult to tell if a no-start from not being able to read a key was due to an issue with the car or interference from an external source.

On a couple other cars I've owned the manufacturer has mentioned not to keep two different keys in close proximity (such as on the same key ring) due to the key having to be near an antenna on the physical ignition switch. That shouldn't be the case with the keyless system in the Focus where they'd have to assume the passenger might have their own set of keys with them.
 
#10 ·
Thank you for this info. I was wondering about the 'electronic' key system, with no mechanical backup. As an avid kayaker, I was curious what would happen if my fob ever got wet, shorted out the battery, and stopped working. It would be friggin' criminal if there was no way to start your car because your key got wet! I mean, kayaking aside (yeah I know, use a dry bag...), what would happen if you got caught walking in a downpour and became soaking wet? You wouldn't be able to drive home?
 
#11 · (Edited)
If the battery went dead or the electronics died in the key fob the active low-power transmitter likely wouldn't work (i.e. you wouldn't be able to leave the key in your pocket and start the car) but the passive, backup RFID-type chip doesn't require any power from the key fob battery and appears to be a separate chip. In the scenario you described you'd have to use the physical key blade to open the driver's door and then hold the damaged/dead fob up against the knock-out plug on the steering column so that you're close enough that the transceiver in the column can power and read the backup RFID chip. You'd then use the keyless "start" button on the dash just as normal to turn the car on.
 
#13 ·
BTW, this type of thing is standard on most "keyless" systems.

My Corvette has the keyhole on the trunk (above the lisence plate) and there is a pull tab in the trunk to open the driver door. The Fob hole is in the glove box.

On other cars the Fob hole can be in the center console. The new Fusion covers up the external keyhole (still in the drivers door) with a removable plastic piece that look like it's the "stationary" part of the driver grab handle.
 
#22 ·
How often should the the key remote battery be replaced. I had my previous VW 5 years and never had to replace but it was the switch blade not smart key.
I haven't seen anything on expected battery life but I'd be surprised if it didn't last at least a few years. The key is referred to by Ford as being passive and doesn't actively transmit anything (which would likely be the greatest power drain over time) until it receives a request from one of the three PATS (passive anti-theft system) antennas in the car. This would be at engine start and at some periodic interval afterwards to ensure the key is still in the car, such as when a door is opened.

The shop manual shows the key has to be within three feet of a PATS antenna to be read, so it is likely an extremely small transmitter power for little coded pulse the key has to transmit. Pressing one of the lock/unlock/hatch/panic buttons on the fob would use significantly more transmit power due to range needed away from the vehicle. Also when using the door handle mounted sensors to open the car instead of using the key fob button may also save and prolong battery life since the key can respond with a much lower transmit power to a request from the car to unlock the doors.
 
#25 ·
RFID tech is apparently being used here. In which the transmitter in the vehicle emits RF radiation (no not the scary stuff) that excites the RFID receiver in the fob. The car is wirelessly powering the fob sort of like that cordless iPhone charger you all saw a few years ago, although at a much smaller power level.

I assume the buttons are the only thing that uses the battery.
 
#30 ·
Yes and no. The keys use the 433 Mhz or 315 Mhz band and when you touch the start button or a door handle the car "pings" the key on a frequency. There are probably 4 antenna in the car, and based on the keys ping responses the car knows the physical location of the key. If it's outside on the right, and that door handle was used it unlocks, the same for being on the left with the left door handle. The start button should work if the key is inside the car. The battery does help power that transmitter (that responds to the ping) but it only does so in the form of amplification (as in the op-amp needs the battery). Without the battery the range on the RF is VERY VERY small, hence the slot in the column. There is typically a coil around those slots and with the coil you can detect the miniscule RF range that the unamplified key has.

The buttons on the fob work mostly in reverse, they send the keycode to the car, who verifies the rolling code and then proceeds to unlock or lock the doors. The same was true of the "chipped" key when you stuck the key in the ignition, the RF coil around the key slot communicated with the key to verify that it is indeed learned to that car.
 
#31 ·
I Am glad I found this
During a sync update ( which frickin weeklY!!!) I got locked out. I eventually got in and got the car started but didn't know about the putting the fob in the hole where the lock used to be.