Hi Liam,

The DDE can prevent regeneration for certain faults, and i'm sure a significant number of faulty glow plugs is one that would. However, mine has one faulty plug and still regens so it has to be more than one!

As far as I know the system uses a combination of EGR & glow plug activation to increase combustion temperature during regen, so faulty plugs could be hampering this.

To regen the coolant has to be over 75 degrees, the pre-cat exhaust temp over 240 degrees, a minimum of 10ltrs of fuel in the tank and a road speed over 60kph.

Have you checked the exhaust temperature sensor (does it give a sensible engine off/on reading) and that the cat isn't blocked also?