Diesel Particulate Filter Efficiency Below Threshold (Bank 1)
What it means
The engine computer has detected that the diesel particulate filter (DPF) is not trapping soot as it should, usually because the pressure difference across it is lower than expected. This most often means the filter is cracked or damaged inside, or the differential pressure sensor or its hoses are giving a false reading.
Related lights
Dashboard lights that may come on with this code.
Symptoms4
- Check engine light on, sometimes together with the DPF warning light.
- Black smoke from the exhaust under acceleration in some cases.
- Limp mode with reduced power on some vehicles.
- Failed emissions test.
Possible causes6
- Cracked or melted DPF substrate after an overheated regeneration.
- Cracked, disconnected or blocked differential pressure sensor hoses.
- Faulty DPF differential pressure sensor.
- Exhaust leak ahead of the filter or between the pressure pickup points.
- Sensor hoses installed in reverse after a previous repair.
- Filter removed or tampered with while the original engine software remains.
How to diagnose5
- Read all stored codes and address any differential pressure sensor code such as P2452 to P2455 first.
- Watch the differential pressure reading on a scan tool at idle and at higher RPM; a reading near zero under load points to a damaged filter or a disconnected hose.
- Inspect the sensor hoses for damage and confirm they are connected the right way around.
- Check the exhaust for leaks ahead of the filter.
- Look inside the tailpipe; black soot after the filter suggests a cracked filter.
How to fix5
- Replace a split or blocked hose and reconnect it the right way around.
- Repair any exhaust leak ahead of the filter.
- Replace the differential pressure sensor if it is proven faulty.
- Replace the DPF if it is cracked, after fixing whatever caused overheating or heavy soot loading.
- Clear the codes, reset the DPF values with a scan tool, then drive and confirm the code does not return.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
In the Saudi market: SAR 150–12,000 (≈ USD 40–3,200)
Our prices come from the Saudi market, converted at a fixed rate (SAR 3.75 per USD). Prices in your country may differ a lot, so we show the cost level.
The cost is low when a sensor hose or the sensor itself is at fault, and reaches the upper end when the DPF is replaced; filter prices vary widely between genuine and aftermarket parts.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026
Frequently asked questions
Does this code mean the filter is clogged?
No. It usually means the opposite: the filter shows less restriction than expected, which happens when it is cracked or when the pressure reading is wrong.
Can I drive with this code?
You can drive carefully for a short time, but a damaged filter lets soot through and can foul sensors downstream, so repair it soon.
Should I replace the filter right away?
No. Check the sensor hoses and the sensor first; they are cheaper and cause the same code often.
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