Citroen C3 2004 central locking issue.

[Jordan8w]

Hello all, I've got a problem with the central locking on a Citroen c3. The interior lock button in the centre of the dash operates the central locking perfectly. However, using the buttons on the key does not. I have repeatedly tried BSI resets, resynchronizing the keys, and even programmed 2 new keys to the car. I have used a frequency detector and can tell that both the new and old keys are giving out a signal but there is no response from the car.

I've found online a separate issue with the central locking (where the care locks but doesn't unlock) which is caused by a relay in the BSI. Is this relay possibly the cause of my fault also?

Any help appreciated.

[Paul-R]

I would think it more likely to be the sensor coil in the ignition key surround. But how to test before replacing I don't know.

[ozvtr]

No. If the button on the dash works then it's not the "relay problem".
Unless you know exactly what you are doing, after market (Chinese) fobs wont work.
You can only use the original fob(s).
Have you tried an absolutely brand new, out of the packet, battery in the fob?
If you use the button on the dash to lock the car, will the fob unlock the doors?
Warning!!! Put a window down before fiddling with the central locking, lest you lock yourself out! Always ensure the drivers door key lock works!!!! It can rust up!!

[ozvtr]

I would think it more likely to be the sensor coil in the ignition key surround. But how to test before replacing I don't know.

The receiver for the remote central locking is a module in the top of the COMs unit (the control unit with the wiper and lights stalks). It's called the HF module.
Coincidentally that module does connect to the coil around the ignition switch but that coil only detects the RFID chip in the key.
So if the module fails, the engine wont start. The poster didn't mention that they couldn't start the car. So I would assume the module is OK.

[Paul-R]

You're absolutely right. My bad. I don't know why I was thinking there was a starting problem.

[Jordan8w]

I would think it more likely to be the sensor coil in the ignition key surround. But how to test before replacing I don't know.

The receiver for the remote central locking is a module in the top of the COMs unit (the control unit with the wiper and lights stalks). It's called the HF module.
Coincidentally that module does connect to the coil around the ignition switch but that coil only detects the RFID chip in the key.
So if the module fails, the engine wont start. The poster didn't mention that they couldn't start the car. So I would assume the module is OK.

The car does start and both the old and new key fobs are sending signal. If I lock the car with the button on the dash I still can't unlock it with the key fob.

[ozvtr]

How long has the fob not been working?
Any work done to the car at that time?
Try putting the fob on top of the steering column shroud and pressing the buttons.

[Jordan8w]

How long has the fob not been working?
Any work done to the car at that time?
Try putting the fob on top of the steering column shroud and pressing the buttons.

I tried putting on the shroud and still nothing. No work done just thought the key battery had died, replaced it and still nothing.

[Jordan8w]

How long has the fob not been working?
Any work done to the car at that time?
Try putting the fob on top of the steering column shroud and pressing the buttons.

Oh and it's been around 2 months now of not working

[Jordan8w]

For anyone wondering, or experiencing the same issue, today I have found out that the vehicle is not seeing the signal from the key fob via diagnostic live data. I believe the Comms unit has the HF module in it and I am going to attempt to get a new comms unit and see if it fixes the issue. I will post results here.

In the mean time if anyone knows anything that I don't please reply if you think it's something else.

[Jordan8w]

Update, turns out the vehicle is recognizing the button press to a degree. I can hear a relay click inside the car when using the old key lock button, however, still not locking. I believe the issue is BSI related, however, the car isn't worth spending loads of money on so I am instead going to wire up an aftermarket central locking system to the dash button.

[ozvtr]

Have you installed or is there an after market radio installed?
From your PM it sounds like something is screwing up the VAN BUS.

[ozvtr]

Either way remove the radio (either stock or after market).
Pop the bonnet, remove the key and close up the car. Don't lock the car (hmmm you cant, LOL).
Wait 60 seconds, disconnect the battery +.
Disconnect the radio from the electrical loom. Close up the car.
Reconnect the battery +.
Wait 60 seconds.
Try the fob.

[Jordan8w]

I've given up on it and purchased a £12 after market lock system. Any chance you know which wires lock and unlock the doors?