Tech advice: how to approach DPF faults

A step-by-step guide on retaining DPF maintenance work in your garage

Tech advice: how to approach DPF faults
Credit: Bigstock.

Designed to collect and dispose particulate matter produced during the combustion of the diesel fuel/air mixture, DPFs became part of the MOT in February 2014.

Technical advisor, Stuart Still of European Exhaust and Catalyst (EEC) told GW: “If DPF light is illuminated, the DPF will need to be regenerated.

“The manufactures handbook explains that the vehicle will need to be driven for about 20 to 25 minutes at over 2500 RPM.

“If the EML comes on and the glow plug light flashes then you will not be able to regenerate the DPF by driving.”

The combination of the DPF and EML light will engage ‘limp mode’ with a maximum of 3000rpm.


EEC DPF toolDPF regeneration and fault finding can be carried out with EEC’s DPF diagnostic tool, designed to help technicians retain DPF maintenance within their workshop rather than having to go to the main dealer.

The tool will reset the DPF light after the DPF has been replaced, reset the additive level and can initiate a forced regeneration.

EEC advises technicians to first check the pressure sensors, which can suffer from a build-up of water.

Initial checks

Stuart said: “Examine the pressure pipes for damage, these must be clean or could freeze in extreme temperatures due to condensation build up.

“Check that the EGR system is clean and working correctly, check that the vehicle has the correct specification engine oil and check the fuel additive Eolys/Cerine.”

If the DPF fails to regenerate due to engine related faults or driving practices and fills to more than 90 per cent or 45 grams, EEC say that it will need to be replaced.

“The ECU must be reset followed by a forced regeneration when a new DPF is fitted to ensure that the ECU knows that the DPF and all related sensors are reset,” Stuart added.

Why DPF might fail to regenerate
  • If the EML is on.
  • Faulty EGR valve.
  • If there is less than 20 litres of fuel in the tank or the fuel light is on.

It is possible to carry out a forced DPF regeneration by using the correct diagnostic machine.

Depending on the vehicle, this operation could be static or dynamic and could take up to 40 minutes.

EEC has an extensive range of DPFs and is campaigning to educate and train technicians to better understand, evaluate and diagnose emission problems.

Stuart said: “The introduction of type approval for catalytic converters has been a great leap forward and has created a level playing field.

“EEC has invested heavily in our own wash coating facility in Denmead, this is to ensure we produce a top quality product for our home and export markets.”

For more information contact Duncan Richards or Stuart Still on 023 9224 5300 or click ‘more details’ below.

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