Emissions

P2002 — Diesel Particulate Filter Efficiency Below Threshold

Severity: medium Drive with care, to a shop

What P2002 means

A diesel engine control unit monitors the particulate filter (DPF) using differential pressure, exhaust temperatures and calculated soot load. P2002 sets when the filter appears to trap less soot than expected. The cause can be a damaged or hollowed-out filter, a faulty sensor, or false readings from leaks in the lines.

Symptoms

  • Check Engine or DPF warning light on
  • Limp mode or reduced power
  • Poor acceleration
  • Smell of diesel soot from the exhaust
  • Frequent regeneration attempts and higher fuel use
  • Visible smoke from the tailpipe

Possible causes

  1. Failed regenerations caused by repeated short trips
  2. Filter loaded with ash or damaged (cracked, melted, or gutted)
  3. Faulty differential pressure sensor or clogged or cracked hoses
  4. Faulty exhaust gas temperature sensors
  5. Exhaust leak before or after the filter
  6. Injector, EGR or boost problems producing excess soot

How to diagnose

  1. Scan for codes and freeze frame data, and look for related injector, EGR or boost codes
  2. Read soot load, ash load and differential pressure at idle and under load
  3. Test the differential pressure sensor and inspect its hoses and fittings for blockage or cracks
  4. Compare exhaust temperature sensor readings with actual temperatures
  5. Inspect the exhaust for leaks and damage
  6. Check sensor wiring and connectors for corrosion or breaks
  7. Verify that regeneration conditions can be met with the owner's driving pattern
  8. If data looks normal, inspect the filter itself and measure backpressure

Common fixes

  • Forced regeneration or professional filter cleaning
  • Replace the differential pressure sensor or its hoses
  • Replace an exhaust temperature sensor or repair its wiring
  • Fix exhaust leaks and the causes of excess soot
  • Replace the particulate filter if it is damaged or cannot be cleaned

Questions and answers

Can I drive with a P2002 code?

For a short time, if the car runs normally. Don't put off diagnosis, because the filter can clog further and power may be limited.

Will a highway drive clear P2002?

If the cause is a clogged filter that never gets hot enough, a long steady drive may trigger regeneration. If a sensor failed or the filter is damaged, the code will return.

Do I always need a new DPF for P2002?

No. First check the sensors, hoses, leaks and regeneration conditions. Replace the filter only if it is physically damaged or can't be cleaned.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.