Particulate filter light, limp mode and oil level rising
- Make and model
- Dacia Duster
- Year
- 2015
- Engine
- 1.5 dCi 110 (K9K)
- Fuel
- Diesel
- Mileage
- 120,000 km
Customer complaint
The particulate filter warning came on twice in a month, then limp mode. The car does short trips in town. The oil level is above the max mark.
Fault codes
Measurements and live data
| Parameter / measurement | Measured | Expected |
|---|---|---|
| Coolant temperature after a 15-minute drive | 68 °C | about 85–95 °C |
| Distance since the last completed regeneration | 1,100 km | normally a few hundred km |
| Oil level and smell | 8 mm above max, smells of diesel | between min and max |
Tests performed
- Coolant temperature graphed on a road testNever passes 70 °C and drops when coasting
- Thermostat removed and tested in hot waterStuck partly open
- Forced regeneration after the repairCompleted normally, soot load back down
Solution
Root cause
Thermostat stuck partly open: the engine never got warm enough to finish a regeneration, so the filter loaded up and fuel from the interrupted regenerations diluted the oil.
Repair
Replaced the thermostat, changed the diluted oil and filter, ran a forced regeneration with the scan tool and a road test. Advised the owner to take a longer drive every couple of weeks.
Parts
Thermostat and seal, coolant, oil and filter
Labour time
1.5 h
Lesson learned
Before cleaning or replacing a particulate filter, find out why it does not regenerate. Coolant temperature is the first thing to check.
Training case: the usual fix for this fault, not a confirmed repair on a specific car.
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