P2002 — Diesel Particulate Filter Efficiency Below Threshold (Bank 1) — LLY / LBZ / LMM Duramax
Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010. DPF codes apply to LMM only; LLY/LBZ have no DPF hardware.
What it means
P2002 means the ECM judges DPF filtering efficiency below threshold using pressure/temperature data. On this platform DPF codes apply to LMM only; LLY/LBZ have no DPF hardware.1
Most likely causes
- Excessive soot loading / clogged DPF from incomplete or interrupted regenerations. — High soot mass raises differential pressure and lowers efficiency; regeneration frequency codes are DPF-specific on this platform.2
- DPF differential pressure sensor / tubing fault giving false efficiency low. — Erroneous pressure readings cause the ECM to calculate low efficiency. DPF monitoring uses pressure/temperature data.1
- Faulty DPF temperature sensors leading to incorrect regeneration control. — Temperature input errors affect soot burn calculations; efficiency judged by pressure/temperature data.1
- Excessive oil ash accumulation from engine oil consumption or wrong oil. — Ash permanently fills DPF volume, reducing filtration efficiency over time. DPF is present only on LMM.1
How to diagnose
- Verify sub-engine: confirm LMM 2007.5–2010; LLY/LBZ have no DPF and P2002 does not apply.
- Scan for companion DPF codes (e.g., P2459 regeneration frequency) and check freeze frame for mileage/load.
- Check DPF differential pressure sensor readings at idle and under load; inspect pressure tubes for soot blockage or leaks.
- Check DPF temperature sensor values vs. expected during regen; compare bank 1 sensors.
- Review recent drive cycles for completed regenerations; frequent regens suggest excessive soot/oil ash.
Common mistake to avoid
Cleaning or replacing the DPF before checking its pressure sensor and tubes. Cracked, melted, plugged or wet sensor tubes, or a failing sensor, can set DPF codes while the filter itself is fine. They are cheap to check; clear and verify them before touching the filter. Source: FleetRabbit — P2002 DPF efficiency code causes and fixes.
Parts and tools you may need
- OBD-II scanner with GM enhanced PIDs
- DPF differential pressure gauge
- Digital multimeter
- Inspection mirror / borescope
- Service information for LMM DPF pressure/temperature specs
Tools you’ll need
- OBD-II scan tool — Reads P2002 and companion DPF codes plus freeze frame to confirm LMM application and recent regen/load conditions.
- DPF differential pressure gauge — Verifies actual DPF restriction vs. sensor data to distinguish clogging from sensor/tubing faults.
- Digital multimeter — Tests DPF pressure sensor supply/ground/signal voltages and temperature sensor resistance to find electrical faults.
Rough cost and difficulty
| Likely repair | Parts | Shop labor | Who usually does it |
|---|---|---|---|
| Scan-tool forced (parked) regeneration | — | 0.5–1.5 hrs | DIY with tools and a manual |
| Exhaust gas temperature sensor | $50–$250 | 0.5–1.5 hrs | DIY with tools and a manual |
| DPF differential pressure sensor | $80–$300 | 0.5–1.5 hrs | Easy DIY |
| DPF professional cleaning (bake and blow) | $300–$700 | 1–3 hrs | Shop |
Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.
When to see a pro
If DPF is removed or modified, professional restoration to OEM emissions configuration is required for legal operation and monitor readiness. If differential pressure remains high after confirming sensors, professional evaluation of DPF condition and regeneration history is needed.
Check for recalls
Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.
Sources
Spotted an error, or something missing? Tell us
Run a LLY / LBZ / LMM Duramax? This goes straight to the editor — it is not published.