Effective DPF diagnostics is fundamental to providing a right-first-time solution.
By assessing the mileage and information gathered by diagnostics, it should be possible to determine whether a DPF is blocked with soot, for which a forced regeneration could be sufficient, or ash, in which case the DPF requires removal and cleaning.
Whilst driving style and, in particular. urban usage is the biggest cause of filter blockage, it’s also vital through detailed diagnosis to eliminate other causal issues, i.e. sensor failure or EGR problems.
The blocking of Diesel Particulate Filters are a source of continued problems for a high % of diesel drivers. Normally, difficulties are brought about by the vehicle being used mainly within the urban environment and therefore stopping the passive regeneration process to operate.
Owners expect their garage to resolve the problem, but often there is a gap in knowledge and experience of DPF’s and therefore the default answer is often to replace the filter. This is particularly common in the Main Dealer environment and is wrong, unless the internal monolith is broken up. Replacing the DPF when not needed is at a significant and unnecessary cost to the customer.
DPF’s can be regenerated or cleaned either on or off the vehicle. If the filter is significantly blocked or has high ash content, then the only way to clean and restore the DPF is by off-vehicle cleaning.
Soot and Ash and are fundamentally different materials, but they both accumulate in the DPF. Soot can normally be removed from the DPF through regeneration, which burns it, Ash on the other hand, is incombustible and can only be removed from the DPF by cleaning off-vehicle.
Owners and indeed Garages often think a regeneration is an automatic quick fix, only to find the customer returns after a few days or weeks with the same issue. This is indicative of not thoroughly diagnosing the problem.
The regeneration process can be aided by the application of specialist fluids that work as a catalyst to aid and accelerate the burn-off process, usually through lowering the temperature at which the trapped soot burns
Everyone is aware that diesel emissions and their particulate matter is carcinogenic.
There is concern in the industry that carrying out a static regeneration of a DPF, (as opposed to driving at highway speeds) has further serious health implications. The emissions during regeneration are particularly hazardous and, when done in the static environment, are not being adequately disbursed.
There is plenty of evidence of regenerations being carried out close to public areas and even, quite incredibly, within the workshop. It’s also of great concern when static regenerations are carried out at customers’ houses, clearly without a risk assessment as to public access and ventilation.
The ability to do static regenerations is a diagnostic trick and although there appears to be no specific legislation that currently stops them taking place, it is potentially in violation of the Clean Air Act.
To highlight the lack of realisation as to the dangers of the emissions, it’s becoming regular practise to stand at the back of the car and video the regeneration or cleaning process, ready for social media!
The simple test is to ask: “Would I let my kids stand next to a car having a static regeneration?”
Garage owners clearly have a duty-of-care to protect their employees and the public. Therefore, they should carry out and document a procedure for DPF regeneration
and decide whether static regeneration is appropriate, in the environment that it is to be carried out in.