DPF warning light: what it means and what to do
The DPF warning light is one of the more specific dashboard warnings your diesel can show. Unlike the engine management light, which covers dozens of possible faults, the DPF light has one job: telling you that your particulate filter is blocked and the car cannot clean it on its own.
The short version
Here is what it means in plain terms, and what you should do about it.
What the light looks like
The DPF warning light is usually orange. It shows a small rectangular icon, representing the filter housing, with a series of dots flowing beneath or through it, representing particulate matter. Some manufacturers style it slightly differently, but the filter outline and dots are the consistent elements.
If you are not sure whether what you are seeing is the DPF light or something else, check your vehicle handbook. It will have a full list of dashboard icons with descriptions. The DPF light is usually listed under emissions or exhaust system warnings.
On some vehicles the light comes on alongside the engine management light. On others it appears alone. Either way, the message is the same.
What it means
Your DPF works by trapping soot from the exhaust gases. Periodically, the car attempts to burn off that soot through a process called regeneration, raising exhaust temperatures high enough to convert the soot to ash. This typically happens automatically on faster roads.
When the DPF warning light comes on, it means regeneration has not happened as it should. The filter is carrying more soot than it can handle through normal driving, and it needs intervention.
At this stage the car has usually already tried and failed to regenerate. Continuing to drive normally, especially on short trips or at low speeds, will not help. The conditions for regeneration (sustained high speeds, high exhaust temps) simply do not occur in stop-start or urban driving.
What to do
The advice you will often see is to take the car for a long motorway run. In some cases, where the DPF is only lightly loaded, this can work. The sustained high-speed driving creates the conditions for a successful regeneration, and the light clears itself.
But if the light has been on for more than a day or two, or if you have already tried a longer drive and the light has come back, the filter is too heavily blocked for passive regeneration to work. At that point the only reliable options are a forced regeneration (which requires specialist diagnostic equipment and does not always succeed on a heavily blocked filter) or a chemical flush.
A chemical flush dissolves the accumulated soot deposit rather than burning it off. It works on filters that are too blocked for regeneration and does not require the car to be driven to a garage.
Manchester DPF Cleaning carries out mobile chemical flush cleaning across Greater Manchester. We come to you, connect to the vehicle, and clean the filter on-site. Fixed price: £275. Call 0161 694 7331 to book.