Diagnostics · 5 min read
DPF problems explained for diesel drivers
A diesel particulate filter traps soot from the exhaust and periodically burns it off. When that burn-off can't complete, soot builds up and the car starts complaining.
How regeneration works
The car raises exhaust temperature to burn trapped soot into ash. Passive regeneration happens naturally at sustained speed; active regeneration is triggered by the engine management and needs the car to keep running for ten to twenty minutes.
Cutting a regeneration short — switching off partway through a journey — leaves soot behind and stacks the problem up over time.
Why short journeys cause trouble
A diesel doing school runs and short town trips around Stockport may never get hot enough for long enough. Over months the filter fills, and eventually the DPF light comes on.
If your mileage is mostly short and local, a diesel may simply be the wrong tool for the job.
What the warning light means
A steady DPF light usually means the filter is partially blocked and the car wants a sustained drive to clear it. Additional lights, limp mode or a smell of hot exhaust mean it has gone further and needs looking at.
Ignoring it can turn a forced regeneration job into a filter replacement, which is a substantially bigger bill.
What we do about it
We read the stored codes and live data — soot loading, differential pressure, exhaust temperatures — to see whether the filter is genuinely blocked or a sensor is reporting incorrectly. The fix depends on which it is, and we explain that before anything is authorised.
Bookings
Book your car into the workshop
Tell us your registration and what the car is doing. We'll come back to you to confirm a date.