Carlo wrote:The auto electrician has verified (maybe) that the button works. There is probably a problem between the button and the control unit.
He says that to understand and repair the fault it is necessary to disassemble the whole dashboard. I don't want, for a small problem, to risk breaking something else.
Are there other intermediate control unit?
They just wanted to get rid of you, you need to find a proper auto eletrician to diagnose it and show him this:
It's very simple thing, basically just a switch which either provides a high or low signal to locking module on grey/green wire. You just need to check for continuity on that cable from switch to plug, see at what state that signal is and whether changing it locks the system or not. If it does then you have an issue within the switch itself or ignition switch which provides the ground, if it doesn't then module is faulty. No need to tear the whole car apart
1997, 4.0 LWB X300 - Unlucky car but still a daily driver.
1988, 3.6S XJS - Never ending restoration project.
1994, 3.2S X300 - Accident damaged, October 2015. Gone!
1994, 3.2S XJ40 - Long gone.