Clogged DPF, how to diagnose it?

DPF (Diesel Particulate Filter) is a particulate filter that is used in diesel cars to reduce the emission of harmful particulate matter (PM) into the environment.

The DPF works by absorbing particulate matter, which is created when diesel fuel is burned in the engine, and storing it inside the filter. The particulate matter is regularly removed from the filter through a thermal process called regeneration, where the filter is heated to a high temperature, causing it to burn.

The most common errors accompanying DPF filter failures

Diesel Particulate Filter (DPF) related faults generate numerous DTCs. Below are the most common errors:

1. Errors indicating DPF blockage:

P242F : Excessive soot in the DPF filter.

P2002 : DPF filter efficiency too low (Bank 1).

P2003 : DPF filter efficiency too low (Bank 2).

2. Errors related to DPF regeneration:

P244A : DPF regeneration system efficiency (Bank 1) - too low.

P244B : DPF regeneration system efficiency (Bank 1) - too high.

P2458 : DPF regeneration takes too long.

P2459 : DPF regeneration too frequent.

3. Pressure difference sensor errors:

P2452 : DPF differential pressure sensor problem - low signal.

P2453 : DPF differential pressure sensor problem - high signal.

P2454 : DPF differential pressure sensor - low input.

P2455 : DPF differential pressure sensor high input.

4. Exhaust gas temperature sensor errors:

P0544 : Exhaust gas temperature sensor problem (Bank 1, sensor 1).

P0546 : Exhaust gas temperature sensor - high signal.

P2031 : Exhaust gas temperature sensor problem (before DPF).

P2033 : Problem with exhaust gas temperature sensor (after DPF).

5. Fuel/AdBlue quality errors affecting DPF:

P229F : NOx sensor problem (affecting DPF efficiency).

P20EE : Insufficient efficiency of NOx reduction system – impact on DPF.

P207F : AdBlue quality incorrect - may affect DPF regeneration.

6. General errors related to the DPF system:

P141F : DPF filter function problem – emission limit exceeded.

P2463 : DPF soot level too high.

P246C : The differential pressure sensor indicates a problem with DPF performance.

P24A4 : Problem with reading the pressure difference or temperature in the DPF system.

7. Errors with cooperating systems:

P0299 : Insufficient turbocharger boost - impact on DPF efficiency.

P0101 : Air flow sensor (MAF) problem - DPF regeneration disturbances.

P0401 : EGR flow too low - affecting DPF load.

Common causes of DPF errors:

1. DPF filter blockage:

Short routes, no possibility of full regeneration.

Excessive soot due to a faulty injection system or turbocharger.

1. Sensor malfunction:

Damaged differential pressure sensor or exhaust gas temperature sensor.

1. Abnormal regeneration:

Contamination of the intake system or faulty injectors.

1. Fuel problem:

Poor quality fuel or AdBlue (in vehicles with SCR).

DPF diagnostics:

The main parameters you need to check are the differential pressure on the DPF filter read by the so-called "differential", DPF back pressure (most often BMW cars), temperatures on the DPF filter and the calculated mass of soot and ash. The limit parameters may differ for each car, so it is worth monitoring the normal operating conditions of your DPF on an ongoing basis, e.g. thanks to dedicated applications or universal diagnostic testers such as SDprog.

Regular diagnostics and maintenance of the DPF system, as well as monitoring the soot level in the filter, can prevent more serious breakdowns and costly repairs.