Jimmy from O’Rileys Autos investigates a 2015 Citroën DS5 suffering from recurring DPF issues despite multiple previous cleaning attempts. By using live diagnostic data to identify ash saturation over soot accumulation, the video demonstrates why off-car machine cleaning is often the only permanent fix for high-mileage diesel vehicles.
The vehicle arrived at the workshop with 104,000 miles on the clock, displaying both engine management and service lights, alongside a “risk of particle filter clogging” warning.
The owner reported a frustrating cycle: the DPF had been cleaned twice by mobile services, only for the fault to return within 50 miles.
Jimmy noted that while the previous cleaners successfully reset the light, they failed to identify the underlying cause of the rapid soot or ash accumulation.
Initial diagnostics were performed using the Kingbolen K8 Pro.
While the tool identified DPF overloaded and clogged codes, the breakthrough came from analysing the exhaust line live data.
The scanner revealed that the vehicle had successfully completed a regeneration only 60km prior, yet the differential pressure remained stubbornly high at 34 mbar.
Jimmy explained that this specific data point is critical for technicians.
Because regeneration burns off soot but cannot remove ash, high pressure immediately following a regeneration indicates either a physically damaged DPF or a filter saturated with non-combustible ash.
At 104,000 miles, the latter was the prime suspect, leading to the decision to remove the unit for machine cleaning rather than attempting another on-car chemical flush.
Once removed, the DPF was placed on a Carbon Clean DCS16 machine. The cleaning process immediately flushed out a significant amount of “red sandy ash”, a typical byproduct of the fuel-borne catalyst (PAT fluid) used in PSA-group vehicles.
This gritty substance cannot be cleared while the filter is on the vehicle, as it requires high-pressure reverse flushing to be removed from the inlet face.
The repair also addressed the vehicle’s additive system. Investigation revealed that the PAT fluid (Eolys) tank was likely empty, having never been refilled since the car was new.
After the cleaned DPF was refitted, the team topped up the additive reservoir and programmed the fill into the ECU.
Post-repair testing showed the idle pressure had dropped to a healthy 4 mbar, confirming the blockage was cleared.
