If you’re diagnosing a DPF fault, it’s important to note that there are a number of components used in the control of soot combustion (not just the DPF). Faults with any of these components will either result in the DPF becoming blocked, or will lead the ECU to think that the DPF is blocked when it’s not. Below is a handy checklist of components which should be checked to ensure they’re operating correctly before assuming a replacement DPF is required.