Jaguar XJ40 Central Locking Not Working
On the XJ40 dead central locking is most often the locks falling out of step, or one sticky door that can't finish its stroke, so the system gives up with a click. I'd start free: charge the battery, test the door-lock fuse and resync by working the plungers in order. Then find the door that lags and free it, or fit a cheap aftermarket actuator.
How bad is it · Safe to drive
Safe to drive; lock the doors by hand
The car drives normally and each door still locks with its plunger or key. A door stuck locked or one that won't lock is a security problem, not a mechanical one.
Which one applies to yours depends on your symptoms, your model year and what has already been done to it.
Likely causes, most common first
Read the check cost before the odds: a free check that rules a cause out beats a likely guess that costs money.
Locks out of step with each other
The front actuators report whether their door is locked; the rears don't. If a door didn't finish its last stroke, the control unit stops driving the locks and you hear only a faint click. It often follows a disconnected battery, a jump start or work inside a door.
Nothing locks centrally, or only a faint click, yet each door still locks with its own plunger or key. It started after the battery was off, the car was jumped or a door was worked on.
Sit inside with all doors shut. Work each plunger up and down a few times and leave it up: front passenger, rear passenger, rear driver, driver last. Then try the key or the console switch.
The plunger sequence brings it back; repeat it if needed. Another way: lock the driver door with the key, push the other three down by hand, then unlock with the key. If it keeps falling out of step, one door isn't finishing its stroke and its linkage needs attention.
A sticky lock or actuator that can't finish its stroke
The actuator only gets power for about a second. Old grease or a dry linkage slows it enough to stop the lock halfway, and one lagging door upsets the other three.
Clicking from the doors but the plungers barely move; one door locks but won't unlock, or closes and springs back. Worse in cold weather or after the car has stood.
Feel each plunger by hand and open the stiffest door first. With the door card off, lift the rubber boot on the actuator shaft and look for water inside.
Spray into the actuator under the boot and onto the linkage, then work the lock up and down a couple of dozen times. Do all four doors while you're in there. WD-40 frees it; a dry PTFE spray or graphite lasts longer. A smear of grease on the actuator piston lasts longer than a spray alone.
A dead door actuator
Each actuator is a small reversible motor with a gearbox, not a plain solenoid. The motor seizes or wears out its brushes, and that door stops responding while the others carry on.
One door does nothing electrically while the rest lock and unlock. Its plunger still works by hand, perhaps stiffly. Doors that lock and unlock on their own often point to a failing front actuator.
Take the actuator out but leave it plugged in, then operate the locks: if it runs, the fault is in the linkage. Off the car, put 12 V across its two motor wires, one way to lock and reversed to unlock; on the front doors these are purple/pink and purple/orange.
Generic 5-wire actuators fit the front doors and 2-wire ones the rears, on the original mounting holes. Cut off the Jaguar plug and solder by function, for example purple/pink to green, purple/orange to blue, the third purple wire to brown, yellow/orange to white and black/pink to black. Map the wires with a 9 V battery and a meter before soldering, as colours vary between years. Used actuators of the same age tend to fail again quickly. A front lock unit can be changed without taking the window out: a small ratchet spanner reaches its bolts by feel. A weak original can be split along its glued seam to clean the motor, then taped shut.
A flat battery or a blown door-lock fuse
Low voltage leaves the lock motors too weak to move. The doors and boot share one 15 A fuse, so a single shorting actuator or loose wire blows it and every lock goes dead.
No door moves any other and there's no clicking; the battery has been running low, or the fuse blows again as soon as you lock.
Charge the battery fully. Test the door-lock fuse in the right-hand footwell box with a test lamp, not just by eye. If it blows straight away, look for a burnt actuator or a loose wire before fitting another.
Charge the battery, replace the fuse and repair any loose wiring. If the remote misbehaves after a new fob battery, it needs re-syncing to the car. Worth trying for repeat failures: a 10 A in-line fuse on each door's actuator feed, so one bad motor can't take out the rest. With the battery flat and the boot locked, charge it through the positive jump post on the bulkhead under the bonnet, and the locks come back with it.
The door lock control unit, its plug or its earth
The door lock control unit sits on the component panel under the passenger side of the dash, with a white 9-way plug. It takes 12 V on pin 1 and earth on pin 2 and sends pulsed lock and unlock signals on pins 3 and 4. A dirty plug or a corroded earth stops it as surely as a dead unit.
Each door still works by its own plunger, the fuse and battery are good, but nothing happens centrally; or one door behaves differently from the rest.
Pin 1 should show 12 V. Check pin 2 for continuity to a good earth; if jumping pin 2 to earth makes the locks work, clean its earth stud in the right footwell. Unplug and replug the connector; if that helps, clean the contact edges with a pencil eraser.
Clean the plug and the earth first. If the unit itself has failed, a used one swaps straight in.
A rear lock that pops up and drops back: latch or linkage play
On unlock the rear plunger rises partway and falls back to locked. Usually the actuator is fine and the stroke is lost in a worn plastic link or a tired latch.
A rear plunger jumps half up and drops back, often after an outside handle was replaced, or only in cold weather. A spare actuator changes nothing.
Run the window down, take the door card off and watch the link from actuator to latch while someone unlocks. Look for a loose S-hook, a wobbly plastic link or a latch that feels stiff by hand.
Take up the play with an extra metal clip on the plastic link, or a small cable tie round the S-hook and link, and lubricate with graphite. If the latch itself is at fault, the whole latch assembly is changed, with the window frame partly out.
A front lock switch that doesn't report the door's position
Besides the motor, each front actuator has a switch that tells the system whether the door is locked. If it doesn't make contact, the other doors won't follow the key, and a faulty one in the driver's door can keep blowing the fuse and burning out the rear actuators.
The driver door locks with the key but the others stay put, while the console switch or the passenger door still moves everything. Or new rear actuators die again soon after fitting.
Try the console switch and the passenger door. If they move the driver lock, the wiring is fine and the switch inside the driver's lock is the suspect. On the front actuator plug, pins 1 and 2 are the motor and pins 3 to 5 the position switch.
Replace the front actuator, or the whole driver's door lock assembly. Fitting new rear actuators alone won't stop it coming back.
A previous owner's add-on remote or alarm wiring
Dealer and aftermarket remote kits were often spliced into the lock wiring with snap-on connectors, and a failed control unit was sometimes bypassed with a relay. A corroded splice or a half-wired bypass looks just like a dead actuator or unit.
Remote lock works but remote unlock does nothing; or the console lock button closes the windows but not the locks. Cut wires or extra relays behind the passenger knee panel.
Take off the passenger knee panel and look at the lock control unit's plug for cut wires, snap-on splices and extra boxes.
Replace snap-on splices with soldered joints. If the original unit was bypassed, fit a working one and restore its wiring.
The key locks but won't unlock: the key doesn't match the locks
With Tibbe locks almost any key will turn to lock, but only a key that matches the lock's discs will unlock. A swapped ignition barrel or a replacement door handle with its own barrel leaves key and doors mismatched.
The key locks every time and never unlocks; the console switch and plungers unlock fine. Door handles or the ignition lock have been changed at some point.
Try every key you have, including the original that came with the old ignition barrel, if it's still around. The valet key in the green holder locks but never unlocks.
Use the key that matches the door locks, or recode the door and boot barrels to the ignition key. Jaguar service bulletin 76-64 covers Tibbe door lock repair.
The boot or fuel flap won't follow the doors
The boot has its own lock actuator, driven by the same lock relays as the doors, and its key cylinder has three positions. Turned fully clockwise it stays locked whatever the central locking does; fully anticlockwise it stays open; upright it follows the doors. A gummed-up boot actuator or a latch that has never seen grease stops it just as well.
The doors lock and unlock normally but the boot doesn't, or it opens only with the key or the glovebox release button.
Set the boot key upright first. Then take off the boot lid trim, find the actuator's black 4-way plug and put 12 V across its purple/orange and purple/pink wires, reversed to unlock. The release actuator on the brown 2-way plug is a separate part, worked by the glovebox button.
WD-40 into a sticky boot actuator brings it back. For a lasting fix drill out its rivets, clean and grease the inside and close it with small nuts and bolts, about half an hour. A seized latch frees with penetrating oil through the access hole behind the number plate, given a few soaks over a day.
A cracked solder joint in relay module G or behind the fuses
The lock and unlock relays sit together in relay module G, on a blue 20-way plug behind the panel under the passenger dash, and each fuse box is a stack of soldered boards. A dry joint on either board cuts the locks while every fuse tests good.
Relays click but nothing reaches the doors, or the dash reports a circuit fault for one fuse box with no blown fuse in it.
Test each fuse with a meter or test lamp and reseat it. Then open relay module G and look at its joints under a magnifier; moving the relay by hand shows whether the relay or its joint is at fault.
Worth trying: reflow the cracked joints. While the panels are off, clean every earth from the bulkhead back to the boot.
The order to check them in
The point of the order is money: each step either rules a cause out or makes the next one worth doing. Green is free, amber costs a little, red is the one to arrive at last.
Try each door on its own
Work each plunger, and the front locks with the key. If every door moves by itself, the fault is shared: battery, fuse, sync or the control unit. If one door won't move, start there.
freeCharge the battery and test the fuse
Use a test lamp on the door-lock fuse in the right-hand footwell box. A fuse that blows again at once means a short, not a bad fuse.
freeResync the locks
All doors shut, work each plunger and leave it up: front passenger, rear passenger, rear driver, driver last.
freeFree the stiffest door
Door card off, spray the actuator under its rubber boot and the linkage, and work the lock a couple of dozen times. Check for play in the links.
a can of lubricantTest the suspect actuator
Leave it plugged in and run the locks, or put 12 V across its two motor wires both ways. No movement means a dead actuator.
freeCheck the control unit plug and earth
White 9-way plug under the passenger dash: 12 V on pin 1, good earth on pin 2. Look for snap-on splices from an old remote kit.
freeBoot left behind: check its key position
Upright follows the doors. If it still won't move, test the boot actuator at its 4-way plug behind the lid trim.
freeReplace the actuator
A generic 5-wire unit for a front door, 2-wire for a rear, soldered in by function.
an aftermarket actuatorThe fuses named above — where they sit
The highlighted position is the one the procedure talks about. Pulling a fuse is a stop-gap, never a repair: check what the circuit feeds before you pull it.
Circuit descriptions from the Jaguar fuse tables, 1993 edition. Drawing by jagaux.com from the factory electrical guide. Fuse layouts change between model years — read the legend on the lid of your own box before pulling anything.
What it usually isn't
Don't spend money here first:
If none of this finds it:
On jagaux.com
- Jaguar XJ40 FUSE 1 or FUSE 2 FAIL WarningIf the fuse warning comes on with the locks dead.
- Jaguar XJ40 Battery Drain, Flat After a Few DaysIf the battery keeps going flat and the locks lose sync.
- XJ6 (XJ40) fuse boxesWhich circuit each footwell fuse feeds, other years from the same page.
- Jaguar XJ40 Door Handle Repair, Door Won't OpenIf a door won't open because its handle, rod or latch has failed.
- Jaguar XJ40 Window Motor, Windows Not WorkingIf the windows are dead along with the locks, or one window clicks but won't move.
- Jaguar XJ40 Immobiliser Problems, Won't StartIf the remote won't code or the alarm won't disarm.
- Jaguar VIN decoderConfirm your exact model year, engine and factory options before ordering parts — free.
Ratings, fuse numbers and torque figures vary by model year and market. Read the legend on your own car before pulling anything, and use the figures in the manual for your car, not the ones in a video.
Check your VIN: exactly which car you have and which bulletins apply to it.