When you open your door do you hear the "bing bing bing" sound as if you still had your keys in the ignition?
If you are hearing the "bing" noise then there is a good chance the switch in the bottom of the ignition barrel is stuck which basically means the car thinks your keys are still in the ignition, so when you turn key in your door it only locks that door and not the rest. From another forum:
Symptoms:
1) Warning beep that the ignition key is still inserted when driver's door is opened
2) Radio remains on when key is removed from the barrel
3) Unable to lock the car with central locking - either on remote or by using the key in the door
Diagnosis:
The ignition barrel thinks the key has not been removed when it has.
There is a white plastic rod in the ignition barrel which is pushed by the inserted key pushing against a switch contact in the rear of the housing that takes the ignition barrel. This rod sticks due to dirt and debris in the barrel and does not spring back when the key is removed.
Things to try:
Disconnect the battery for a few seconds and then you'll be able to use the central locking to lock the car; you'll need to do this each time you leave the car.
Try blowing compressed air down the barrel to blow away any debris
Try blowing brake cleaner down the barrel
Temporary Fix:
Remove the ignition barrel:
Remove upper steering column shroud nearest to the dashboard only by undoing two screws; you need to turn steering and remove the two round plastic screw caps
Install the ignition key and turn it to position 1
Insert a thin bladed screwdriver in the square hole in the top rear of the ignition barrel to release the barrel
Pullout the ignition barrel using the key
At the back of the ignition barrel: Remove the black plastic retainer, return spring and white rod from the ignition barrel; blow air down the back of the ignition barrel to clear debris; spray cleaner down rear of barrel; clean the parts and assemble.
It was a surprise how much dirt and large pieces of junk came out.
Permanent Fix (well until next time it gets clogged):
Get a new barrel using your key number for around £70 incl VAT
You COULD have found the same advice inside 2 min if you had searched, September 2016
