I've posted something similar recently. My original headunit didn't work or power up at all in my car, so got an aftermarket one put in which stopped my central locking working. The aftermarket one worked fine though. Bought another original with warranty so I could get central locking back BUT that won't work either. I've checked all fuses, it's cracking me up now, I'm no good with wires etc :( any ideas?

it will be the wire for the stereo diagnostic if I remember right.. cant remember the colour tho  that would cause the central locking issue with the after market one

When you said it did not work at all did you mean no signs of life at all with the ignition both on and off?

 

This thread explains most pit-falls with after market units:-

http://www.briskoda.net/forums/topic/99785-help-k-line-ign12v-swap/

 

Summarising, you need to swap over the  permanent and switched 12V feeds; You need to feed power to the aerial; Don't plug into the diagnostic port until you have made these changes or you will cause damage.

 

The only common link I can find between the radio and central locking is Fuse 10. This feeds the radio and the convenience system which includes central locking and the diagnostic port . If this has blown you may also find you have lost the front interior light.

 

 

I'm just trying to get an original one back in, it won't work at all. I took the aftermarket one out & central locking works fine now.

Broken wire somewhere if all fuses are ok. Multimeter needed i think to check for power.

I'm sure there was a cut wire that's tucked up, it's an ex taxi been told they cut wires for their meter or something? God knows, I'll get a multimeter..thanks