good thought Jaye

The BCM has no bearing on this circuit.
the 5v reference is from the PCM, try onitoring is & tapping the PCM
how high does it spike?

just a thought, check the supply to the EFI relay under the bonnet, i have seen an issue with the connector in the relay block, its a double ended female spade terminal from the power bus bar to the relay. i have had to lift the fusebox & solder the bottom end of this to the busbar.

Rob

I find it mildly amusing when someone posts me a memcal to change for some mods they have done & its from one of those Ebay "tuners", i wont name him but think 3 letters & 3 numbers... read off the tune & find its one of mine, the slack prick didnt even bother to remove the lit...

umm im pretty sure its a serial data signal

The Circuit is pretty simple, the fault WILL be in this circuit. The hard part is being an intermittant fault. all i can suggest is DO NOT fit new earths or replace wiring, chances are you will create more issues. follow the diagnostic exactly, if it is not an int code you will find the fault. Discl...

heres a couple

get me a list of bins you want & ill see what ive got.

Rob

here is a good copy

i still id most of them in a hex editor... hard to break old habits.

Rob