Central Locking Troubleshooting

What is the central locking doing?

Pick the closest match.

Nothing works: check power first

If no door responds and you hear no relay click, the control unit has no power, or no ground.

1. Check fuse 27 (30 A). It feeds central locking and also the interior lights, the radio memory and the on-board computer. If those are dead too, the fuse is blown.
2. The control unit is powered through the interior light control module, which the factory diagram shows the locking feed passing through (cavity 3). A fault in that module or its connector cuts the locking power as well.
3. With a helper operating the lock, listen at the control unit for relay clicks. The control unit sits in the driver's side footwell area on many cars. Check where yours is.
4. At the control unit, check for battery voltage on pin 3 (1.5 mm² feed) and a good ground on pin 4, which goes to the ground splice and on to G200.

Wiring and help: Central locking, 4 door · Central locking control · Fuse 27 detail

Some doors work, others do not

The control unit is working, so the problem is at the door that does not respond: the motor, its wiring, or the lock itself.

1. Operate the lock and listen at the door. A faint whirr or click means the motor is trying.
2. Check for a stiff mechanism. After many years without lubrication the lock linkage can bind enough to stall the motor.
3. Check the wiring in the rubber boot between the door and the body. The wires flex every time the door opens, and they break there. Look for a broken or frayed wire, and check for continuity from the door plug into the door.
4. To test the motor, disconnect it and touch 12 V across its lock and unlock pins briefly, then reverse the polarity. A good motor moves each way.

Wiring and help: Central locking, 4 door · Rear doors, boot and fuel flap

Works one way but not the other

The control unit gets its signal from a switch built into the driver's door lock, and from the key. If only one of those works, the fault is in the switch or its wiring.

1. Driver's door: the lock motor assembly contains a switch that tells the control unit to lock or unlock when the key is turned or the safety catch button is pressed. Check its connector and wiring, including the door boot.
2. Passenger side: the key switch in the passenger door has its own contacts. Check it the same way.
3. A signal that works one way points at one of the two lock or unlock wires, not the power.

Wiring and help: Central locking, 4 door

Boot lid or fuel flap only

The control unit drives the boot lid motor and the fuel flap motor on their own wires, so the doors working means the unit is fine.

1. Check the wiring in the boot lid hinge area. The boot lid wiring flexes constantly, so wires crack there.
2. The boot lid motor is grounded through the ground splice near the control unit. Check that connection.
3. Test the motor with 12 V as for a door motor.

Wiring and help: Boot lid and fuel flap motors

Locks itself, unlocks itself, or clicks at random

A control unit that fires by itself usually has moisture in it, or is getting a false signal.

1. The control unit can unlock all the doors automatically after a crash, using an inertia switch. Check that its wiring is sound.
2. Check the control unit for moisture. Water can get into the unit and its plug from a leaking door seal or drain. Look for green deposits on the connector and the circuit board.
3. Look for a damaged or shorted wire in a door boot that is feeding a false signal.