Right then had a think and a fiddle the sensors are not earthed via the bolt or anything else multimeter showed this to be the case

Also there are no metal to metal joints on the sus to go back to earth all bushed

the only thing i can try now is that the sensors do and can rotate a little once the bolt is loose approx 3mm either side so will have a check of these and report back

James, I've 2 spares ecu's so thanks

Paul