Code
P242F
ISUZU
P — Powertrain
DPD Restriction
Views:
UK: 18
EN: 44
RU: 23
AI status
Completed
Completed
100%
Causes
- Soot-clogged or ash-loaded DPF/DPD (normal regeneration not completing)
- Failed or out-of-spec differential pressure (DPF) sensor
- Faulty or contaminated exhaust temperature sensors (upstream/downstream)
- Stuck or malfunctioning EGR causing excess soot production
- Exhaust leak or restriction upstream of the pressure sensor (manifold, turbo, catalytic)
- Failed turbocharger (reduced combustion temperature / improper regen conditions)
Symptoms
- MIL/check engine light on with P242F stored
- Reduced engine power or limp-home mode
- Frequent or failed regeneration attempts; prolonged active regen
- Increased fuel consumption
- Visible black smoke from exhaust during acceleration
- Unusual exhaust odors or overheating underbody near DPF
What to check
- Read freeze frame and full scan tool data; note conditions when code set (engine load, RPM, temperature)
- Check for additional DTCs (EGR, turbo, temperature sensors, pressure sensor circuits)
- Monitor live data: differential pressure across DPF, inlet/outlet exhaust temperatures, soot mass (if available), boost pressure
- Visually inspect wiring and connectors for DP sensor and temperature sensors for damage or corrosion
- Inspect exhaust for leaks or physical damage upstream of the DPF (manifold, downpipe, turbo)
- Perform smoke test on intake/exhaust for leaks that affect combustion or sensor readings
Signal parameters
- DPF differential pressure (kPa) — expected low at idle, rises under load; abnormal high indicates restriction
- Exhaust gas temperature (EGT) inlet and outlet (°C) — should rise during regen; failed sensors may show implausible values
- Soot mass or DPF load (%) if supported — high values indicate required cleaning or replacement
- Turbo boost/boost pressure (kPa or bar) — low boost with high backpressure can indicate DPF restriction
- EGR position/command vs actual — stuck/open EGR increases soot production
- Regeneration active flag / regen duration — repeated long regens indicate poor clearing
Diagnostic algorithm
- Connect a diagnostic scan tool, record freeze-frame and stored faults. Note conditions when P242F set.
- Review related DTCs (EGR, temperature sensors, boost, pressure sensor). Repair any upstream faults first.
- Inspect wiring and connectors to the differential pressure and exhaust temperature sensors; repair any damage.
- Monitor live data: confirm DP sensor readings change with engine speed/load and that inlet/outlet EGT behave plausibly during a manual/forced regen.
- Verify EGR operation and intake system for leaks or causes of excess soot production; repair if malfunctioning.
- Attempt a forced regeneration per manufacturer procedure while watching differential pressure and temperatures. If regen completes and DPF load reduces, retest drive cycle.
- If differential pressure remains high during and after a proper regen, perform a backpressure test or remove and inspect the DPF for heavy soot/ash, physical damage, or contamination.
- If sensor(s) are out of specification, replace the differential pressure sensor and/or exhaust temperature sensors and re-test.
- If DPF is mechanically blocked, ash-loaded beyond service limits, damaged, or contaminated by oil/coolant, follow manufacturer guidance for cleaning or replacement.
- After repairs, clear codes and verify normal operation over a full drive/regeneration cycle.
Likely causes
- High soot loading in the DPF from repeated short trips or failed regen
- Differential pressure sensor drift or failure
- Exhaust temperature sensor fault causing false regen logic
- EGR malfunction increasing soot production
- Physical blockage or damage of the DPF (collapsed substrate or heavy ash)
Fault status
Status
DPD/DPF restriction detected — excessive backpressure or abnormal DPF sensor readings. May cause reduced engine performance, failed regeneration, and possible limp mode until resolved.
Repair difficulty: Hard
Diagnostic time: 2-6 hours
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