Originally Posted by Flux Capacitor

Ok, it has its own ground because the cossie normal ecu ground can vary
due to injector peak currents and wiring voltage drops in these conditions.
If there wasnt a seperate ground, the coil would missfire as the ground
of the ecu moves around 0.5volts during various conditions due to the trigger
signal being only a 5 volt (TTL) signal as is very suseptible to electrical
noise and disturbance.

Hope that explains things.


Simon