I've had my XJ Sovereign 2.7 diesel (x358) for three and a half years and 20,000 miles and didn't even know that I had a PDF until my son's Volvo had a problem which developed on a long run down to Devon and cost him over £2,500 for a new PDF. Having spent all that money he then sold it and bought an S type which developed a PDF problem and had it changed. Now 2,000 miles later 4 hours into a long run to Wales the 2 lights came on, it went into limp home mode, he called the AA who hooked up a laptop and cleared it. It appears that his engine management unit does not automatically clear the DPF. Having researched prices on the web, I see that new PDFs are only circa £150. Is this correct and has anyone changed themselves on either an XJ Sovereign or an S type?