Before you chase a central locking fault, it helps to know what your car should have. The owner threads are clear on the basics, though a few details are disputed and are marked below.
Which cars have what
- NA: an alarm, but no central locking. The fob arms and disarms the alarm (the indicators flash), and there is an alarm LED on the dash. The doors are locked with the key. Owners who wanted remote locking on an NA have fitted it afterwards. See Fitting central locking.
- Turbo: usually has remote central locking, but owners say not all Turbos had it. One owner with a 2003 Turbo found no door wiring, rubber bungs in the door holes, no backup battery and no switch on the steering column, so it probably never had it.
- A quick check for central locking: a lock/unlock rocker switch on the steering column cowl. Another owner says all UK VX220s have an alarm.
The parts
- Alarm module: under the dash. It takes the fob signal and sends a "lock" and an "unlock" pulse to the central locking. One owner found it on the opposite side to where the workshop manual says it is.
- CDL (central door locking) module: a small plug-in unit behind the light switch cluster that drives the door motors. It is the most common failure. See CDL module replacement and Central locking faults.
- Door lock motors: one in each door, working on a lock mechanism separate from the key barrel. One owner describes a white plastic part with a hole in its end that hangs vertically from the lock.
- Steering column rocker switch: locks and unlocks the doors from inside.
- Backup battery and "secret button": lets you unlock with the fob when the main battery is flat. See Central locking backup battery.
- Siren: self-powered, with its own rechargeable battery.
The door key and central locking
The key barrel and the central locking are separate. One owner who looked inside a door says the barrel only pushes a set of rods to the normal latch, while the central locking works a separate deadlock point on the lock. Owners generally agree that once the car is locked with the fob, the key does nothing. One put it that the key lock is "useless when the car is locked with the fob", and said this was the reason for the emergency backup battery.
Owners differ on the detail. One says some cars let the key work and some don't, depending on whether the central locking was fitted at the dealer or the factory. That is hearsay and nobody confirmed it.
Some Turbos have the driver's key hole covered by a little black disc or sticker. Peel it off and you find a normal key lock. One owner reports it took him about five years to find out.
Testing the alarm and siren
One owner's test for a car with an alarm: arm it with the fob (two flashes of the indicators), wait about 60 seconds, then open a door. The siren should sound. If the indicators flash but nothing sounds, the siren is the first suspect.
- The siren says "self powering coded electronic siren" on its label. One owner says the original has four wires (earth, live, switched live and a serial communication wire) and is sounded by a coded command, so it needs the original type. Another says it isn't coded to the alarm module and you can just swap one over. Owners differ, so treat a non-original siren as unproven.
- One owner suspects a worn siren battery could drain the main battery. That is a guess, not a tested result. See Flat battery and charging system.
- If one of your fobs doesn't work, one owner says the duff one may need to be re-trained to the car from a working fob. The thread doesn't give the procedure.
- An alarm specialist that several owners recommend has experience of the VX alarm and sells replacement parts and new units (Abacus).