Diesel Particulate Filter Efficiency Below Threshold (Bank 1)

The DPF catches soot from diesel exhaust and burns it off during regeneration cycles. The PCM watches the pressure drop across the DPF — there should be very little when it's healthy. If the pressure differential is wrong (too high = clogged, too low = cracked/missing substrate), or regenerations aren't completing, P2002 sets. On a deleted DPF (illegal in most areas), the PCM sees no restriction and sets this immediately.

Differential pressure across the DPF is outside the expected range for current exhaust flow, OR successive regen attempts failed to drop soot loading.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 1Read DPF soot load and ash load. If ash is over manufacturer limit (often ~100 g), DPF needs cleaning or replacement.
2. 2Compare delta-P sensor reading at idle vs at 2500 RPM. Should rise smoothly with flow.
3. 3Inspect delta-P sensor hoses — they clog with soot.
4. 4Check for forced regen capability with scan tool — attempt one and monitor EGT and soot load.
5. 5If regen completes and soot goes to zero but code returns — suspect the sensor or cracked substrate.

• DPF substrate cracked, melted, or removed
• DPF differential pressure sensor failed or hoses clogged
• Repeated failed regens (short trips, bad EGT sensor, sticking EGR)
• Excessive soot from a fueling problem (bad injector, low boost)
• Cracked exhaust between sensors

$200 (sensor) to $4,000+ (DPF replacement). Professional DPF cleaning $400–$800.