Clogged DPF

QMy son is having trouble with his 56-plate Skoda Octavia 2.0 diesel with the VRS engine. A diesel specialist has diagnosed a clogged DPF and cleaned it for him. Since then, it drops into ‘limp-home’ mode fairly regularly. The garage has said that it has been ‘re-chipped’ in the past and is basically passing the buck back to my son.

Do you think a new DPF would cure the problem? Would remapping of the ECU help? Would a full diagnostic check be in order, although I’m assuming the diesel specialist has already done this? Can you think of any other likely causes? My son says there’s oil coming out of the turbo, but the diesel specialist said it’s not bad and isn’t likely to be the cause.

Gary Mills

AIt would be good to know the original symptoms displayed by the vehicle. The first move would be a diagnostic check to code-read the system. If the ECU has been remapped then this may need to be set back to its original parameters, however this is dependent on the nature of the original problem. Given that the vehicle does have a DPF I assume this hasn’t been cut out. This would be the most likely reason for the remapping of the ECU, although as this is the VRS version it would already have a higher BHP.

The relevance of the oil coming from the turbo does depend on the quantity. While it is common to have a certain amount of misting in the turbo and intercooler pipes, this should not be excessive. One of the most common reasons for a diesel to go into ‘limp-home’ mode is when the sensor detects overboost; this is likely to happen with a turbo which is clogged-up.

One possible scenario is that the diesel specialist has read an overboost code and assumed that the DPF was blocked. Having cleaned the DPF without rectifying the problem – if this was the original problem – they are now backing out of the job.

To summarise, I think the best course of action would be to have an independent diagnostic check, retrieve any codes and then act on those codes.