Hi got a 1.4 mk6 petrol fiesta that was working fine one day and then next wouldnt start. Eac fail flashing on the dash and immobiliser light flashing. Car wont even turn over. Had it plugged into my snapon reader and it came up with about 10 codes cant remember them all without plugging it in again. Few codes about accelerator and immobiliser but all of the codes had low voltage at side of them and one code was just fot system low voltage. When i go on live data with the scanner it shows car battery voltage as 1.8 volts which cant be right. The battery is definately charged up. Im thinking its got ecu failure or a power supply problem dodgy earths etc but i dont know where to begin. I know they have problems with the eac system but theres far too many faults for it to just be that

Check the battery directly with a multimeter, and possibly try attaching jump leads via a running motor and rescan the live data, it would also be easy enough to check the earth's aswell they tend to be easy ish to look at.

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Ive tried jump leads no joy its been at a garage for a week and they couldnt figure it out. Where are the engine loom earths im more of a vauxhall guy

That's it I'm not talking to you anymore.:(

Stoney might have a diagram he seems to have a bit of a thing for ford diagrams best hope he has a look over this.

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if ecu is showing only 1-2v, and battery is reading normal, has to be a wiring fault between.

there are a number of earths that could give you this, check the obvious ones coming from battery, if they are good then i would start by disconnecting the ecu and read the voltages at the plugs and work back from there....if the plugs are receiving the correct voltage then reconnect and try again, if they then drop then likely to have a short withing the ecu itself, but would still send it to be tested before condemning.

Any ideas as to which wires i should be checking? Ive not had any luck finding a pin out for the ecu. Does the engine loom earth back to the battery or is it earthed onto the engine

Any ideas as to which wires i should be checking? Ive not had any luck finding a pin out for the ecu. Does the engine loom earth back to the battery or is it earthed onto the engine

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Check for water ingress where the loom connects to the ecu.

Figured out what the problem is but not sure whats causing it yet. Got low voltage to the ecu from the fusebox 1.9v. Bridged in 12v and it runs fine so need to find the cause of the low voltage. Cheers for everyones help so far. Maybe ford people aint so bad afterall :)