Hi. I have a 1989 XJS V12. I'm thinking of buying a 1993 XJS, 6 cylinder, 90K convertible. The owner states that it will not start, the immobilizer is preventing it from starting. He said he took it to a Jaguar dealer, the tech tried to reset the immobilizer module both with the fob, and, with the reset procedure. Neither worked. Is there a way to fix this? Can I buy a used module and install it? Could the problem just be the inertia switch? Haha. Any ideas?

 

Is that a factory immobilizer?
The inertia switch would be a really straight forward check, but the diagnosis overall will be a little more complicated. Check voltage at the ignition switch, starter relay, etc. I would do the regular no-start checks and take the PO's diagnosis with a grain of salt. I'm not saying not to look at the immobilizer, just that the regular no-start stuff doesn't take up much time to double-check.

 

i think the factory immobilizer is lucas electric products.

 

A US '93 is a1992 build. The alarm module is in the right side of the trunk behind the rear light. It has a big white multiplug that connects it to the car.Try unplugging that and see if it will start. When you replug it the alarm will make a noise,5 of them. After each sound press an alarm fob and if working properly the alarm will beep back. This must be done 5 times, even if you only have 1 fob.