Diesel Trouble Codes

P2002 — Diesel Particulate Filter Efficiency Below Threshold (Bank 1) (L5P Duramax)

Diagnostic reference for L5P Duramax 2017–present.

Updated September 2, 2026

What it means

The ECM has determined DPF filtering efficiency is below threshold based on pressure/temperature data. Generic definition: DPF filtering efficiency, judged by pressure/temperature data, is below threshold.1

Most likely causes

  1. DPF is genuinely restricted / soot loaded beyond regeneration capability — Efficiency monitor uses differential pressure and temperature data to judge trapping. Sustained high soot load or failed regeneration can set P2002. Generic definition notes efficiency judged by pressure/temperature data.1
  2. DPF differential pressure sensor or its signal is inaccurate / out of range — Erroneous delta-P feedback can cause the ECM to calculate low efficiency. Platform-specific differential pressure sensor circuit/range performance code exists: P2BAD — Diesel Particulate Filter Differential Pressure Sensor Circuit Range/Performance.2
  3. Exhaust leaks upstream of DPF or poor sensor connections affecting pressure readings — Leaks or connection faults alter measured delta-P, leading to false efficiency calculation. Sensor circuit/range performance issue is documented for this platform.2
  4. Incomplete or interrupted regenerations due to driving pattern / thermal conditions — If normal regeneration cannot complete, soot accumulates and efficiency monitor trips. Generic definition ties efficiency to pressure/temperature data.1
  5. Aftertreatment temperature modeling error from faulty temp sensors — Efficiency evaluation relies on temperature data; inaccurate temps skew the monitor. Generic definition references pressure/temperature data.1

How to diagnose

  1. Verify freeze frame and confirm code is P2002 on L5P Duramax with full aftertreatment set: EGR, DOC, DPF, SCR with DEF. Platform facts confirm emissions hardware.
  2. Check for companion codes: DPF differential pressure sensor circuit/range P2BAD, SCR/DEF codes P204F/P203F/P20E8/P20EE/P2BAD/P2201, boost/underboost codes P0299/P0234. Platform facts list these systems.
  3. Review recent regeneration history and driving cycle; short trips / low load can prevent complete regen. Generic definition ties efficiency to pressure/temperature data.
  4. Inspect DPF differential pressure sensor signal plausibility vs. expected values at idle and elevated flow; compare to P2BAD description of signal outside expected range.
  5. Inspect exhaust integrity upstream of DPF and sensor tube connections for leaks, soot plugging, or corrosion that would bias delta-P. Sensor circuit/range performance issue documented.
  6. Check aftertreatment temperature sensor readings for rationality and compare to model expectations; efficiency judged by pressure/temperature data.

Parts and tools you may need

Rough cost and difficulty

Costs vary by region and labor. DPF service/replacement and aftertreatment diagnostics are typically high-cost items. Obtain local quotes.

When to see a pro

If diagnosis indicates DPF removal, cleaning, or replacement, or requires high-pressure fuel/exhaust work, have a qualified diesel aftertreatment technician perform the work. Do not attempt step-by-step repair of safety-critical systems. Refer to platform facts for L5P hardware.

Sources

  1. Curated DTC seed — L5P Duramax (curated) ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — L5P Duramax (curated) ↩︎ ↩︎

Watch a repair

Third-party videos, not ours — for illustration. Confirm anything against the factory service information for your truck.

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