Is there any chance to compare the resistance of the coil with your friend's P4?
I'd suggest to compare the resistance of the tooth mesh sensor of the RWD shaft as well.
If it's not done already check continuity between the RWD shaft sensor and the P4 ECU connector:
the thin red wire from the sensor is ends at pin#18 in the P4 ECU connector, while
the thin white wire from the sensor is ends at pin#16 in the P4 ECU connector.
Power supply issues can also prevent the P4 unit from normal operation. If nothing else remains,
you can try to check the supply voltage of the unit right after the ignition is turned on.
This may require to remove the central console to have access to the ECU grounding and
the supply connector, located beneath / behind.
The unit gets ground from the floor plate, more exactly from the gearbox tunnel, near to the
gear shift lever window. The supply connector contains six wires:
Amber-Black, Red-Black, Purple-Black, Red, Brown-White and Pink.
Without disconnecting this connector turn the ignition on, and perform voltage measure
between the grounding mentioned above and the pink wire, while the clutch coil is still enabled.
Then repeat the procedure between the same ground and the Red-Black wire.
If you read less than 11V, even momentarily, then it's probably a grounding or supply wiring related issue.
Last edited by LoneWolf33; 28-09-15 at 19:06.