Stuart Still, Technical Trainer for EEC, explains why garages are missing out on a real goldmine when it comes to Diesel Particulate Filter (DPF) replacement and how you go about performing a forced regeneration.

Over the past few months on my visits to various garages and motor factors, I have been asking a couple of questions regarding DPFs, they are: a) “how many do you sell or fit?” and b) “do you actively promote them?”.

The majority of answers were along the lines of: “We regard it as a main-dealer only product and don’t want to get involved with DPFs as it is too complicated.” Another popular reply was: “We just can’t get the supplies” – I was staggered!

I explained that a DPF is only a filter which removes soot/carbon from the exhaust gases, and is very easy to fit. You would never have guessed this however, judging by the fact that main dealers still account for the majority of the DPFs fitted within our market place.

Most of them are chargeable to the vehicle owner, even if they fail within the manufacturer warranty period, and they are regarded in the same way as an oil, fuel, or air filter, as the warranty only covers mechanical failure.

A high ticket product

With that evidence in front of us it is clear that the aftermarket is missing out on an opportunity to increase sales and profit margin. DPFs are a high ticket product, for example an OE Mazda 6 DPF is £1,800, and an OE Vauxhall Zafira DPF costs £750.

In the April edition of PMM, I explained about the different types of DPF, their construction and how they work. This time I thought it may be useful to share information that can help you to feel more confident when discussing DPFs.

How and when to ‘regenerate’

1) There seems to be some confusion about why they fail and how to diagnose faults – it is extremely unusual that a DPF will fail on its own! The problems are usually upstream of the DPF or due to an issue with the DPF system.

2) If the DPF light comes on this means ‘Regenerate’. The majority of vehicles have the same warning light sequence as show in Fig 1 but always check the vehicle’s own handbook to be safe.

3) Once again, read the hand book for instructions, for example: ‘Drive for 20 minutes at a constant speed of 65mph’.

4) If the DPF is not regenerated at this stage and fills to over 90% or 45 grams, the component will need replacing. This is not covered under warranty.

5) If the coil and engine management light is on with a loss of power, ‘limp home mode’ will engage with a maximum of 3000 RPM and the fault code will read ‘DPF soot loading too high’ – a forced/emergency
regeneration is required.

6) In order to carry out a forced/emergency static DPF regeneration, use the correct diagnostic machine.

7) If the engine management light comes on first, followed by the DPF light, it indicates an issue within the DPF system, for example temperature, pressure, sensors etc.

8) Ensure the vehicle is parked outside, in park/neutral, the hand brake is on, engine warm (with at least a quarter tank of fuel) and that there are no fault codes stored. A step- by-step guide is supplied with a suitable reset/regenerate tool (Fig 2).

Useful advice and checks for DPFs

■ Check pressure sensors. There could be a build up of water.
■ Examine pressure pipes for damage. These must be clean or could freeze in extreme temperatures due to water build up.
■ Check that the EGR system is working correctly.
■ Check that the vehicle has the correct spec engine oil.
■ Check the additive (active system) Eolys/Cerine.
■ Fiat has a service indicator which tells the owner they need an oil change after 15,000 miles. They were then finding that if the vehicle had a DPF and was doing lots of regenerations, the oil quality would degrade quickly, meaning the vehicle required an oil change before the advised 15,000 miles.
■ Check the oil levels because some levels can rise due to regeneration as fuel gets into the oil. Oil and oil filter must be changed before replacing the DPF.
■ The ECU must be ‘readapted’ when a new DPF is fitted and also when the fuel additive Eolys/Cerine is topped up.

A DPF will not regenerate:
■ If the engine management light is on for any fault.
■ If there is a faulty EGR valve.
■ If there is less than 20 litres of fuel in the fuel tank or if the fuel light is on.
■ If you drive with your foot on the clutch pedal.