Diesel Trouble Codes

P242F — Diesel Particulate Filter Restriction - Ash Accumulation — 6.7 Cummins (SCR / DEF)

Diagnostic reference for 6.7 Cummins SCR/DEF 2013–present. Focus on confirming ash load service limit and ruling out soot-related restriction before condemning…

Updated October 15, 2026

What it means

Generic definition: DPF ash load has reached its service limit. On the 6.7L Cummins ash does not burn off in regeneration; at high mileage the DPF needs cleaning or replacement.1

Most likely causes

  1. DPF ash load at service limit from high mileage / normal accumulation — Ash is incombustible residue from oil consumption and additive metals; it accumulates over the life of the filter and cannot be removed by regeneration. High-mileage trucks commonly reach the ash service limit.123
  2. DPF face plugging / severe soot restriction mimicking ash limit — Chronic incomplete regenerations, short trips, low exhaust temperature, or upstream faults can load soot heavily enough to trigger restriction codes and high backpressure. Verify soot vs ash before replacement.425
  3. Differential pressure sensor or sensing tubes skewed / blocked — Erroneous delta-P readings can cause the ECM to calculate an artificially high ash/soot load. Inspect sensor, hoses, and orifices for soot plugging, moisture, or damage.56
  4. Exhaust temperature / regeneration inhibit conditions — Low EGTs from VGT sticking, boost control issues, or chronic under-load operation prevent complete burns, increasing soot loading and regeneration frequency.57
  5. Upstream engine/aftertreatment faults increasing soot production — Injector imbalance, EGR valve/cooler issues, turbo performance, or air intake restrictions raise soot output, accelerating DPF loading.4536
  6. DEF/SCR system faults indirectly affecting regeneration strategy — SCR/DEF faults can alter aftertreatment control logic and regeneration scheduling, contributing to abnormal DPF loading patterns.56
  7. DPF internal damage or substrate failure — Physical damage, cracking, or face plugging from foreign material or thermal events can raise backpressure independent of ash mass.26

How to diagnose

  1. Confirm code and freeze frame; check for companion codes P2463, P2459, P2002, P1451, EGT/NOx/DPF sensor codes.
  2. Read live DPF data: ash load %, soot load %, differential pressure at idle and at rated speed, exhaust temperatures pre/post DOC/DPF. Compare to spec.
  3. Inspect DPF differential pressure sensor and sensing tubes for plugging, moisture, or leaks; clean or replace as needed and re-evaluate delta-P.
  4. Perform a controlled road test with scan tool logging to verify regeneration initiation/completion, EGT rise, and VGT vane operation. Note boost and rail pressure behavior.
  5. Check service history and mileage; high mileage with repeated regenerations supports ash service limit. Review oil consumption and oil specification compliance.
  6. If soot load is high and ash load is within range, address root cause of incomplete regeneration before condemning DPF: verify EGR function, turbo VGT actuator/sensor, fueling, and temperature sensors.
  7. If ash load is at service limit and delta-P remains high after confirming sensors and completing a successful regeneration, DPF cleaning or replacement is indicated per Cummins service criteria.

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

Tools you’ll need

Rough cost and difficulty

Likely repairPartsShop laborWho usually does it
Scan-tool forced (parked) regeneration—0.5–1.5 hrsDIY with tools and a manual
DPF differential pressure sensor$80–$3000.5–1.5 hrsEasy DIY
DPF professional cleaning (bake and blow)$300–$7001–3 hrsShop
DPF replacement$1,500–$4,0001–4 hrsShop

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 high-pressure fuel system work, internal engine repairs, or safety-critical systems are suspected, stop diagnosis and have a qualified diesel technician inspect. Do not attempt high-pressure fuel injection service without proper training and equipment.

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

  1. Curated DTC seed — 6.7 Cummins (SCR / DEF) (curated) ↩︎ ↩︎

  2. NHTSA owner report 11674103 ↩︎ ↩︎ ↩︎

  3. NHTSA owner report 11627026 ↩︎ ↩︎

  4. Curated DTC seed — 6.7 Cummins (SCR / DEF) (curated) ↩︎ ↩︎

  5. Curated DTC seed — 6.7 Cummins (SCR / DEF) (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  6. NHTSA owner report 11644228 ↩︎ ↩︎ ↩︎ ↩︎

  7. NHTSA owner report 11680515 ↩︎

Repair videos: P242F on the 6.7 Cummins '13+

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

New RAM 6.7 Cummins DPF SCR Replacement — TDR Auto · 117K views

2022 Ram Cummins DPF Regeneration and Y43 Recall Explained — TheRamGuru · 100K views