my 2005 Mondeo 2ltr tdi runs fine and smooth but if I try and accelerate to pass another vehicle the glow plug alarm comes on and it goes into limp mode which immediately drops the speed which is somewhat dangerous - I've had the fault codes read numerous times and there has not been a definite reason given for what is the problem it's costing a huge amount of money to have the code read but each time the same fault comes back . can anyone help ?