Sorry wrote a great long reply on this iPhone then someone rang with a Mini gearbox question and I lost your reply. Excellent points above, all are valid. Plugging and unplugging and a squirt of contact cleaner in every plug and connector is very good advice. As is checking earths especially ECU multiplug connectors.
Advanced check is to inspect every pin and socket looking for black spots (arcing of low voltage connector remember some only carry 0.8-1.5v) and loose sockets or pins pushed back into the block connector.
Electrics are a bugger to fault trace but don’t forget the basics, battery and running voltages, fuel line pressure, and note all monitor values with your code reader, if it can’t read them there are excellent ones that can for just a few pounds.
You will crack it and what a great learning curve.
BR
Colin
