Emissions

P24B3 — Diesel Particulate Filter Soot Level Moderate

Severity: medium Safe to drive

What P24B3 means

The engine control unit estimates how much soot is in the particulate filter using the pressure drop across it and a calculated model. P24B3 means the soot load has passed a normal threshold but is not yet critical. Normally the filter cleans itself through regeneration, burning off soot at high exhaust temperature, and that has not happened enough.

Symptoms

  • DPF or check engine light on
  • Dash message asking for a highway drive or regeneration
  • Higher fuel consumption during active regen
  • Cooling fan running longer and hotter exhaust
  • Slight loss of power in advanced cases
  • Oil level rising from fuel dilution after failed regens

Possible causes

  1. Mostly short trips that never heat the exhaust enough
  2. Regeneration interrupted by switching the engine off
  3. Passive regen conditions not met (low load, cold weather)
  4. Faulty differential pressure sensor or its hoses
  5. Faulty exhaust temperature sensors
  6. Injector, EGR valve or turbo problems producing excess soot
  7. Wrong or degraded engine oil

How to diagnose

  1. Scan all codes and freeze frame data and look for related engine or exhaust faults
  2. Read soot load, distance since last regen and regen status on a scan tool
  3. Inspect the pressure sensor hoses and fittings for cracks, blockage or leaks
  4. Check differential pressure sensor readings at key-on engine-off and at rpm
  5. Test exhaust temperature sensors and their wiring
  6. Check EGR valve, injectors, turbo and intake leaks as sources of excess soot
  7. Check oil level and condition for fuel dilution
  8. Run a forced regen with a scan tool and compare readings before and after

Common fixes

  • Drive 20-30 minutes on the highway at steady speed for passive regen
  • Forced (service) regeneration with a scan tool
  • Replace or repair the differential pressure sensor and hoses
  • Replace exhaust temperature sensors or repair wiring
  • Fix the cause of excess soot: EGR, injectors, turbo
  • Change oil to a DPF-compatible type

Questions and answers

What does P24B3 mean?

It is an early warning that the diesel particulate filter holds a moderate amount of soot. It is not critically clogged yet, but it needs a regeneration before it gets worse.

How do I clear P24B3?

Drive on the highway at steady speed for about 20-30 minutes, or have a forced regen done with a scan tool. Once the filter cleans, the code usually goes away; if not, look for sensor or soot-source faults.

Can I drive with P24B3?

Yes, for a short time, but do not wait long. As soot builds up, the engine may go into limp mode and repairs get more expensive.

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.