A conundrum. Drove my '96 XJS in the morning, no issues, smooth as ever it was. Later that day, turned on the car, it would not start - turned over, but would not start. Transmission warning light was on, but had not been on previously. Did some research, many pointed to the rotary switch. Pulled the switch, dis-assembled, cleaned the wipers and contacts, did a general once over sealed it up and re-installed. Same issue. Contact from the switch does illuminate the reverse lights in reverse. Checked relays, fuses, etc. Still no solution. Attempted to get some indication of the problem through OBD, but my interface won't connect to the car (!) I never had that problem before... OBD works just fine on another car, just wont connect to the Jag - first time for this, too. Did a hard reset on the electrics, still no start, no OBD... Somebody help me, please.

 

Okay. Found the problem. Lady Penelope mentioned the inertial switch in one of her posts. I must have tipped it while re-installing the interior panels. Reset the switch. It's all good.