you ought to take a look at the double function relay on these as they do give problems with supplying ecu with power.
also take a look at the ecu and check for water ingress.also i think there is a separate earth to the gearbox that brakes off and that is for engine management.
also the inertia fuel shut off connections can give problems.
pre heaters don't activate on these unless its below 0 degrees
ps its worth checking ALL fuses in and under fuse boxes engine bay and under the dash
hope this helps martin