key no longer turns off engine
 

1996 xj12. I have been having some issues with this car. Latest, I pulled the two relays in both right and left hand heel boards to check they were working, as I could not start the car with the key. Anyway, put a new relay in each, turned ignition on, still no crank, but still able to start by jumping across starter relay. NOW, dash lights stay on while engine is running, when key is turned to off position, engine keeps running and dash lights stay on. Removing the two relays in the kick boards shuts down the engine. Replacing the relays after shutdown, all is well, no dash lights on,but put key in ignition and turn, all lights come on and stay on with key removed unless relays are removed again.
Any ideas welcome, please.
Oh I did put old relays back in those positions, still the same problem.

well you idiot, try repeating what you did to create the mess to start with. what a dummy.
yea you fixed it didn't ya. yep I did. good job I can take P out of myself.

Check ALL your ground cables. Some of the issue's with your 96 sounds like bad grounds. If any look swelled just replace regardless of how the ends look. If not report back and we'll try something else.

Hi 1 of 19. I managed to solve this problem. But thankyou so much for responding.
I was wanting to ask you, since you have so many of these cars, have you ever encountered the situation where the ignition key has apparently lost its ability to communicate with the on board computer?
I managed to obtain the Jaguar technical guide which Jaguar supplied to the dealers for their technicians use, and it says that should the key transponder fail, the immobilization system will inhibit fuelling and cranking of the engine via the engine ECM.
It goes on to say it also immobalises direction indicators, windscreen wipers, heated seats, crank relay, gearshift interlock, interior lights.
These are all things which are not operational on this 96.
I am kind of torn on this one as I would have thought that in the event of key failure, although I could crank the engine by jumping the connections at the crank relay position, that there would be no fuel pump operation, and yet, when I do jump the crank relay connections, the engine cranks and immediately fires up and runs great.
Have you any thoughts my friend?

Hi again 1 of 19. Spoke to service tech at Jag dealership today, he says that the 96 model xj12 did NOT have a transponder in the key.
Anyway, I have been looking at grounds, wow there are a lot, and have not seen any bad yet.
Blew coolant system expansion tank yesterday. $300 for new one. That's life. Started car again today after refilling with coolant, and let it run at stationary, so got up to working temp, and electric fans did not come on. Probably reason pressure got too high in cooling system and blew.
Oh some good news, I got passanger side dip beam on today, together with side marker and rear light by replacing fuse in RH fuse box, but then those lights would not go off until fuse pulled.
Good job I can laugh at myself.
I have checked every relay and fuses and fuse positions for power, and all seem good.
Beginning to think it is a module problem.
Jag dealership said they would charge me $140 to do a complete diagnostic.
Would have to get it flat bedded over to them and back when they done with it, but then I should know what problems are caused by.
Before I do, I just bought a new OBD2 scanner, need to read instructions for it, but maybe it will give me some pointers as it says it operates in real time as well as taking saved codes from computer.
My isn't life fun. Unfortunately don't know any Jag techs who would come out to the house.

Richard

Wish I could help but your issue's are ones I have yet to experience.