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Rear doors/locking

Billy Beatnik

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Just recently my two rear doors will not lock or unlock with the remote, I have to push the button on the inside to lock or unlock. No problems with front doors and everything else works fine, no battery issues either. Anyone have any ideas?



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Hello, Watching the replies to this.  I have that problem with one door and it is because the motor unit has failed.  Apparently it is quite a common problem.

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Just to show how hard it is to diagnose without being hooked up to a diagnostic computer this is from a Jaguar Technical Training Manual: If you thought pressing the button just did one thing, think again......


Complex Network Functions

In addition to sharing information, multiplexing has enabled modules to work together to perform complex vehicle functions. The sequence below demonstrates how a network can complete a complex function such as Global Closing using shared logic. The following example depicts an X250 equipped with Passive Entry.

The sequence starts with an operator standing outside of the vehicle (all windows and sunroof open and doors unlocked) with a SmartKey within one meter of the driver’s door handle antenna.

1. Pressing the switch on the driver’s door handle provides a hardwired ‘lock request’ input signal to the keyless vehicle module (KVM).

2. Once the KVM receives the hardwired ‘lock request’ input signal, the KVM then transmits a low frequency (LF) signal to the driver door handle antenna which activates any SmartKey transmitter within one meter of the handle antenna.

3. The activated SmartKey transmits a radio frequency (RF) ‘security code’ signal which is received by the RF Receiver.

4. The RF Receiver transmits the ‘security code’ signal via a dedicated serial data line to the KVM, which checks and validates the security code.

5. Once the security code has been validated by the KVM, the KVM sends the ‘lock request’ signal to the CJB via MS CAN bus.

6. Upon receiving the ‘lock request’ signal, the CJB confirms that none of the latches are ‘ajar’ by monitoring the aperture ‘ajar’ switch signals, which are a direct hardwired input to the CJB.

7. Once it has confirmed that none of the latches are ‘ajar’, the CJB sends a ‘lock request’ followed by a ‘security request’ over the MS CAN bus.

8. Locking and Security Request Results – The front door modules receive the ‘lock request’ signal via MS CAN. The front doors lock. – The front door modules transmit the ‘lock request’ signal to the rear door modules via LIN bus to lock the rear doors. – The RJB receives the ‘lock request’ signal and inhibits the trunk and fuel door release. – Once the vehicle is locked, the CJB automatically enters security mode and sends a ‘security request’ signal over the MS CAN bus, and flashes the front side lights. – The front door modules receive the ‘security request’ signal via MS CAN and flash the side view mirror turn signal and approach lights. – The RJB receives the ‘security request’ signal and inhibits fuel pump driver module operation and flashes the tail lights. – The instrument cluster receives the ‘security request’ signal and activates the security LED in the sunload sensor on the dashboard. If the operator releases the lock button now, the car is locked and armed but the windows and sunroof are still open. By continuing to press the lock button for an additional three seconds, the following events occur:

9. The KVM is still receiving the hardwired ‘lock request’ signal from the driver’s door handle and sending it to the CJB via MS CAN. Once the CJB sees the ‘lock request’ signal for more than three seconds it will send an ‘all window close request’ signal over the MS CAN bus and a hardwired ‘all window close request’ to the sunroof module.

10.The front door modules receive the ‘all window close request’ and close the front windows and transmit the request via LIN bus to the rear door modules to close the rear windows.


The windows and sunroof will only globally close if the anti-trap functionality has been enabled through window / sunroof initialization.


I am quickly coming to the belief that any electrical issues need to be diagnosed fully by someone who knows what they are doing with the appropriate diagnostic hardware/software before setting off on a course of replacing the obvious culprit part.....


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Thanks Guys,

Funnily enough, I know the rear drivers side was working until my son in law started messing about with the button on the door. If I can figure out what the previous message is saying I’ll try to see if I can get it all connected again.

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3 hours ago, Billy Beatnik said:

... If I can figure out what the previous message is saying I’ll try to see if I can get it all connected again.

Simply saying you may well need to hook up to a good diagnostic computer, and know what you are doing to sort it. These machines are very complicated and use multiple computers and sensors talking over several networks to perform what seems a simple function. The modules are sensitive to low voltage causing software problems so probs better to diagnose with the computer rather than chase possible "obvious" fixes.


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I had a similar problem with my 3.0D S. Both the front and rear passenger doors intermittently refusing to lock or open from outside. I replaced the latch assembly on both doors.  Quite expensive at around £150 each. The one for keyless entry has an extra motor. Requires quite a bit of stripping down of the door to replace. Window has to come out as well. Sounds worse than it is but takes a bit of time and fiddling!

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I'm having the same problem with my rear doors. But mine dont unlock or lock at all unless I manually press the lock of on both interior door handles. 

I've been told its something to do with the actuators? But not had it officially diagnosed yet.

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If it is both doors, and the problem did not develop with first one not working then the other it is unlikely to be 2 seperate faults, one on each door, probably a problem in the "computers" or modules.


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Hi all.

I have had the issue with the rear doors failing to lock/unlock, I have the keyless entry type of door locks.

First noticed on the nearside rear when I gave a friend a lift and, the door had to be unlocked manually, as the little lever did not active from the central locking system.

Shortly after that I started to notice the offside rear door not locking and unlocking intermittently, and after a while could only be locked from the inside pushing the little lever in.

I found online some replacement actuators after doing some checking to find out what the problem could be.

Here is a link https://www.ebay.co.uk/itm/232792541799 ,I ordered a left and a right side total charge £124.16 with postage.

I fitted them myself, the first one was a little tricky trying to work out what to do, the keyless entry electric connection stumped me for about 10 mins till I sussed out the workings of it, there is not a lot of room to view things and my failing close up eyesight is a pain in the rear end.

The second one was a doddle now I knew how it all went together, I did not have to remove the windows, though if I remember correctly I undid the bolts that secured the window motor to the mount and this gave enough room to get the door lock assembly out. It took probably an hour each side not rushing at all.

The new ones have been in and working with no issues since October 2019.

I took the old ones apart to be nosey and saw there are 2 small electric motors that operate the mechanisms. I had a look on Ali express and found replacement motors the code numbers are FC280 and FC130 there is 1 of each in the actuator, I bought 2 of each for less than £20 with postage, and have rebuilt the original door actuators ready for if/when they fail again.

Taking the actuators apart is fairly easy I guess, the motors are a push connection no soldering or anything like that, just take note of where everything goes and should be an easy fix.

I did a simple test on the old motors, just ran a 12v battery supply through them, 1 motor did not spin at all, 2 motors turned but not very well and, the last motor span fast and freely, so I think that confirmed the 3 motors had gone past their best.

Hope this helps regards Martin.


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