Respectfully, you clearly aren't a Jaguar mechanic. I am, and have been for over 30 years. I guess I date myself using "mechanic" instead of "technician". LOL
The information you're stating is entirely applicable to the pre-XJ40 cars. Those older cars were incredibly easy to diagnose, but not so for anything built in the last 20 years. I can't tell you how many Lucas M100 starters I've replaced on those older cars, but it is a LOT. Conversely, the number of starters for the newer cars have been relatively few. Once Jaguar got rid of carbs and the early fuel injection systems and went to something reliable and modern, the days of customers cranking their starters until they burned up ended.
The key pick-up for the security system wasn't 100% reliable even in a brand new car in '99. As the car ages, the pick-up moves and the keys get banged up. As a result, they become unreliable. The first sign of a failing key or pick-up is the exact complaint of the original poster. If the problem occurs using the spare key, the pick-up may still be at fault, but you always have the customer test the spare key FIRST because that is the easiest thing to fix and the hardest for a technician to diagnose (customers always present one key when turning in the car for service). If the problem continues using the spare key, you then find out if voltage is going to the starter solenoid (usually not), which then takes you down the usual path of brake switch and neutral switch. The problem is rarely the starter switch itself or the security computer, both of which are in the circuit.
Thursday, July 21st, 2011 AT 8:13 PM