Peter, sorry I’m no electrickery expert or familiar with the GDI however if I had one with your symptoms the first thing I might do would be to ‘make and break’ the BCU connectors a few times to attempt to clean the pins. My Duratec has a MFU which is the for runner to the BCU and I have done this successfully before with my MFU to correct a random instrument fault. Connectors are often the weak link in an electrical system. On the Duratec these connectors also pass the warning light signals to the dash pcb. The current is very low so the pins are susceptible to high contact resistance particularly if there is any damp present. Water does get into this area on the Duratec via the heater drain holes however this may have been improved on the GDI. On the Duratec I get away with ‘hot’ breaking the connectors but to be cautious I would probably disconnect the battery first on the GDI as I suspect there will still be CAN activity with the ignition off, should you decide to do this...
Just a suggestion, good luck!
