Stevie O’Reilly of O’Rileys Autos demonstrates a methodical diagnostic and repair process to tackle persistent DPF faults and severe oil dilution on a 2017 Mitsubishi ASX 2.2 diesel.
The vehicle arrived attempting frequent regenerations, logged with fault codes P2454 (DPF pressure sensor) and P252F (oil level too high). Live scan data showed the pressure sensor reading minus 5 hPa key-on-engine-off, prompting verification with a manometer.
A smoke pressure test identified a leaking injector seal on cylinder two and a slow-leaking boost hose. Stevie noted that filling engine oil directly to the maximum mark on these 2.2-litre units accelerates oil dilution, advising a midway fill instead.
Because DPF removal is highly labour-intensive on this model, Stevie performed an on-car chemical clean. This successfully reduced backpressure from a high reading down to a healthy 50 hPa at 3,000 rpm and 5 hPa at idle, verified on a road test.
To permanently clear the faults, Stevie performed “Engine Oil Exchange Service” and “DPF Exchange Service” initialisations in the ECU, warning that simply changing the physical oil is insufficient to reset the dilution code.
