So have recently purchased a 1.6 2002 MK1 Focus and it's managed to develop an interesting central locking issue. I have looked on search and cannot find anyone describing something similar but feel free to link me to the post if there is one. In short, when I bought the car, the seller made me aware of the fact that the central locking with both the key and the remote doesn't work, ergo, open driver door manually and when inside unlock each of the other doors. They hadn't tried a reprogram or a battery change of the key so after getting a price discount from that issue, I reprogrammed the remote key (key in ignition, position 1-2-1-2 etc). To my surprise it worked!! Over the next few days all was working fine until a day or so ago they remote would only work 1 out of 3 times, and then slowly died out to nothing. Central locking/unlocking still working when using the key in the door itself though. Key fob battery replaced and remote central 'unlocking' works, including boot opening, but will refuse to lock even after reprogramming it a few times just to be sure. When sitting inside and trying to use remote central locking it looks like all the other doors are trying to lock (little lock switch moving to the locked position) but the driver door doesn't seem to budge.

I've just sprayed all the locks, door catches, and door closed sensors with WD40 just incase of water ingress, but any ideas of what could be causing this?

Many thanks in advance!

The main locking servo is in the drivers door and can get water ingress or corrosion over time.

Sent from my SM-G965F (S9+)

I used to have one of these and as I recall there's a small black box with Siemens on it located in the drivers footwell somewhere.  If you unplug it and leave it a few minutes then do the re program key sequence then the central locking will come back.

Thank you both  @Smythson, will try that tomorrow and let you know how I get on. @Stoney871 so far the soaking of WD-40 hasn't worked, is it a case of keep piling it on to help with the corrosion/possible ingress of water? Rather than spraying directly in, is there a certain angle I need to use? Or something a spare morning with a few tools could remove and clean up?

@Darren_Focus when you open the drivers door remove the bottom screw using a or the straw supplied with the WD-40 spray at a 45 / downward angel which is what @Stoney871 meant, also another possibility is that the buttons are wearing out on the fob not the battery / chip board or the transponder but the plagy buttons them self, but before that check the prongs on the battery 1 should be underneath ( which lifts it slightly ) the other at the side ( may have been flattened to the side of the battery over time of changes ) should actually be sitting on top of the battery not the side, if a new fob is required just buy a new key with the same shape blade ( for future use if needed ) with the chip board ( no transponder required then simply swap the chip board from the old key carefully cup the rubber around the transponder and secure it in the new key then just fit the old key to the new fob section 👍 if you're having problems with the boot button inside on the dash pop the button off you'll find a little rubber pad re-glue it aiming very slightly upward so it hits the plates when pushed 👌 yep we own 1 for 4-5 yrs n ive learned a lot about it in 1 yr of self repairing 😀 the plug @Smythson is referring to is on the door side of the drivers footwell just above the accelerator pedal.

Edited April 8, 20188 yr by doggsbody