SPN 3251Heavy truck
HardSPN 3251 — DPF ash load — above threshold
The aftertreatment controller estimates the DPF holds too much incombustible ash (from engine oil and additives). A regen will not clear it—cleaning or DPF replacement is required.
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Likely causes
- Excessive oil consumption feeding ash into the DPF
- Incomplete regens from short urban trips
- Faulty ash-level sensor or calculation model
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Recommended checks
- 1
Check DPF backpressure and regeneration history
- 2
Clean the DPF with an approved method—or replace it if saturated
- 3
Fix the oil-consumption root cause
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Parts to replace
Heavy-duty truck DPF
DPF differential pressure sensor
DEF fluid / additive as required by the system