DPF Warning Light On? What It Means and What To Do

What a diesel particulate filter does

A DPF sits in the exhaust of most diesel cars made since around 2009 and traps soot so it does not come out of the tailpipe. The filter cleans itself by burning the soot off at high temperature — a process called regeneration.

Regeneration needs the exhaust to get properly hot, which usually means 15 to 20 minutes of steady driving at higher speed. Short town trips never get it hot enough, so soot builds up and the warning light comes on.

What to do when the light comes on

Check your handbook first, as the advice varies by make. Many manufacturers suggest a steady drive on a dual carriageway at a constant speed to let the filter regenerate. If the light goes out, the filter has cleared itself.

If the light stays on, the engine goes into limp mode, or other warning lights join it, stop trying and get it checked. Driving on a fully blocked filter can damage the turbo and the engine.

Why filters keep blocking

Repeated DPF problems usually have a cause behind them: a faulty pressure sensor, a sticking EGR valve, a leaking injector, the wrong engine oil, or simply a car that only ever does short trips. Cleaning the filter without fixing the cause means it will block again.

Removing a DPF is illegal on a road car and is an MOT failure. We do not remove filters — we find out why yours is blocking and fix that.

DPF diagnosis in Brierley Hill

We read the fault codes and soot readings, check the sensors and EGR system, and can carry out a forced regeneration or a clean where it will help. You get a clear quote before any work starts. Call 01384 936310.