System service required

Q: I have a problem with a 2006 Volvo XC90 with the D5 engine. I have an issue where, on putting my foot down to overtake after the engine has been on the overrun, I get the warning ‘Engine System Service Required’ and a slight power reduction. Power returns fairly quickly, but the warning will stay, even if read, for a couple of weeks before it goes away again. I have spent some time online looking for answers, but can’t see anything similar. I have tried injector/ fuel system cleaners without making a difference and don’t know what to do next.

I can only think it is similar to an issue I had with a high-mileage 2002 Audi A6 2.5 TDI. The problem there was major loss of power with a warning message, but switching off and on again would clear it. However that used to blow a cloud of smoke, which is not the case here.

I am wondering if it is an issue with oil getting onto a sensor, but don’t know what to do next. Any suggestions as to further diagnostics would be much appreciated. Andy Webb

A: The ‘Engine System Service Required’ message is the equivalent of an engine management light showing. To fully diagnose the problem you will need to read off the fault code to discover what is triggering the light. If you can get the fault codes, I will be able to make a far more accurate diagnosis.

As the fault occurs when trying to accelerate after being on overrun for a stretch, one of the likely possibilities is the boost pressure sensor. Another possibility is a blocked or constricted fuel filter, so if this has not been changed for some time, this would be my first move. I would also check the induction hoses for any signs of leaks – this is often indicated by small patches of oil around the fracture or breach in the system.