I have recently purchased a 2005 focus 1.6 zetec tdci and the engine systems fault message has appeared on the dash and the car wont go over 3000 revs. I took it back to where I got it from and they said they changed the DPF sensor as that's what the fault code told them it was. But since then it the fault message has been coming on and off for a week. I got the AA to check it and they cant find any fault codes when doing a diagnostic test and they say the turbo is fine, engine seems fine, pipes, air filter, and exhaust all fine and was pretty stumped as to what it could be.
Has anyone had a similar problem or has any suggestions as to what this could be?
help would be greatly appreciated