XJR 1999. Faults on dash were gearbox/electrical/immobilizer. No connection to OBD. No ignition light, or start.
By now, I was going through fuses/relays to find a link. Found it in the ECM {engine fuse box 'B' under hood. The relay was not activating, changed it for a new one, no change. Bought a second hand unit. No change. The single relay in box 'B' was not earthing. Put in a temp earth so power to the 4 fuses for gearbox, ecu, security systems.
Still no change.
The car is a project of mine and not used on the road and last week I was resealing around the pedals/sill, right hand side ankle panel. RHD car....So VERY carefully undid the carpet in this area looking g for cut wires or damage. Nothing. I did 'click' the rubber stop under the throttle pedal and found a relay near the heater blower and flicked it a couple of times.
To my frustration I put the key in turned it , ignition, light came on, turned key again, the smooth v8 was rumberling away. What did I do!!!!!!
Anyone have any idea what the connection is?? I think there is a comments earth in this area but I never touched it
Anyone know what happens electronically when the throttle pedal if fully depressed to operate this ' electric rubber stop'
Thanks guys.

 

Also,"wrong part fitted" shown on dash before and after I changed the ECM fuse box