Aftertreatment Diesel Particulate Filter (DPF) Differential Pressure - High
Indicates that the differential pressure across the DPF is higher than expected.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The sensor measures pressure before and after the DPF. If the pressure difference is too high (over 5 inches H2O at normal operating temperature), it means the filter is either clogged or there's a sensor issue.
What the computer is actually seeing
The engine control unit (ECU) sees a differential pressure reading that's consistently above the expected threshold during normal operation, which can lead to reduced engine performance.
What a healthy reading looks like
Expected differential pressure should be less than 5 inches H2O at operating conditions (around 200°F).
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check DPF for physical damage or severe blockage. If blocked, clean or replace it. Decision: Blocked? Yes (replace) / No (continue).
- 22. Inspect the differential pressure sensor wiring and connectors for damage or corrosion. Repair if necessary. Decision: Damaged? Yes (repair) / No (continue).
- 33. Measure the differential pressure using a scan tool or a manometer. If pressure exceeds 5 inches H2O at operating temperature, replace the pressure sensor. Decision: Pressure higher than 5 in H2O? Yes (replace sensor) / No (check for exhaust leaks).
- 44. Inspect exhaust system for leaks before and after the DPF. Repair if any leaks are found. Decision: Leaks found? Yes (repair) / No (perform a forced regeneration).
- 55. Perform a forced regeneration of the DPF. Clear codes and test drive under normal conditions. Decision: Code returns? Yes (further diagnose DPF system) / No (problem solved).
Common causes
- Clogged DPF filter
- Faulty differential pressure sensor
- Exhaust leaks before or after the DPF
- Failed regeneration cycle
- Moisture in the sensor connectors
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Moderate severity means you can drive it for now, but fix it soon to avoid performance issues.
Why does this code sometimes come back after repairs?
If there are still issues with the DPF regeneration or related sensors, the code may persist.
What does this pairing with SPN 4355 mean?
SPN 4355 often indicates additional low-pressure issues, so it’s important to address both codes together.
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