Help please! I'm trying to help out a mate with a non-starting 2006 Focus C Max 1.6 TDCI.

There are no fault codes recorded and the immobiliser light operates normally with either/both keys.

1) The engine does not even attempt to turn over on the key. I have removed relay 13 and found that when bridged the engine will turn over no problems, there is a good 'signal' or energising feed from the ignition in the start position of 12.6v when checked straight to earth. However, on the energising earth side the voltage drops to 8.5v (even straight from the battery). I have checked the black/red wire to the PCM has negligible resistance from relay pin to PCM plug. I reckon there is high resistance (causing the volt drop) in either the PCM or one of the other wire(s) in the coming back out.

My thoughts are if the PCM were cutting the starter relay signal earth as a 'normal' design function (like due to some detected fault or immobiliser issue) there would be no current flow rather than the reduced flow (which I know is the reason why the otherwise good relay 13 is not operating).

Modern Haynes manuals seem less than helpful with only a few bits of very basic generic wiring diagrams which don't even show the correct relay and fuse numbers (maybe they use the same diagrams for everything now to save costs).

2) When I bridge relay 13 above with the key on the start position, the engine turns over fine, but still will not fire (but I imagine the PCM demands an ignition or start feed signal of some kind to start its processes).

I have checked all the relays work when removed and operated across the battery (again limited information on what each relay actually does as the numbers in the Haynes manual and the Ford handbook is incomplete and do not align with the relay numbers and the pictograms mostly just show books with exclamation marks - very helpful, not!).

I have removed and checked all the fuses in both boxes (had to as don't know for sure which fuses cover what circuits as useless information on these too) are good and all the earth points are good too (I even unbolted and cleaned them just to be really sure).

The battery was flat when I first looked at the car and 'engine management fault' would come up on the display when trying to start. Since the battery was recharged the fault message no longer appears. Not sure why the battery was flat - I'm thinking I can look at that once the car is running again.

I am a Truck Technician with auto-electric experience by trade so not totally clueless (tho maybe I am) but struggling to get any decent wiring diagrams or information to work with.

Has anyone experienced anything similar and/or can they tell me where I can get some reliable wiring diagrams and information please.

Thank you.

Julian