Diesel Particulate Filter Efficiency Below Threshold (Bank 1)

What it means

The ECU judged that the diesel particulate filter is no longer trapping soot effectively. On most systems this is based on the differential pressure sensor across the DPF: after a completed regeneration the pressure drop at a given exhaust flow was lower than the minimum expected for an intact filter, which indicates cracked or melted substrate or a leak that lets exhaust bypass the filter. Some newer vehicles also use a downstream particulate matter sensor. Unlike P2463 (soot overload), P2002 points to a filter that passes too much, not too little.

Symptoms

• Check engine light, often with DPF warning lamp
• Visible black or grey smoke under acceleration (normally none with a working DPF)
• Soot deposits inside the exhaust tailpipe
• Reduced power or limp mode on some vehicles
• Frequent or failed regenerations, higher fuel consumption

Common causes

1. Cracked or melted DPF substrate from an uncontrolled regeneration (excess soot ignited at once) or from engine oil/fuel entering the filter
2. DPF removed or gutted by a previous owner (illegal), or a low-quality aftermarket filter
3. Leaking, cracked or disconnected differential pressure sensor hoses giving a false low pressure drop
4. Faulty differential pressure sensor with offset drift
5. Exhaust leak between the turbo and the DPF or at the DPF clamps
6. Faulty exhaust gas temperature sensors leading to overheating during regeneration

How to diagnose

1. Read DPF live data: differential pressure at idle (healthy filter typically 2-10 mbar), at 3000 rpm no load (roughly 20-60 mbar depending on model), calculated soot load, ash load, km since last regeneration and number of failed regenerations. A pressure drop near 0 mbar at 3000 rpm points to a hollow or cracked filter or a sensor hose fault.
2. Key on, engine off: the differential pressure sensor must read 0 mbar plus/minus 2 mbar (approx. 0.5 V on most 5 V sensors). An offset means the sensor is drifting and should be replaced before condemning the filter.
3. Inspect both pressure sensor hoses and pipes for cracks, soot blockage, heat damage and correct routing (front and rear ports are not interchangeable); blow through them to confirm they are clear.
4. Inspect the DPF and the exhaust from the turbo rearwards for leaks, loose clamps, repair welds or signs of tampering; look into the tailpipe for soot. A sooty tailpipe on a DPF-equipped car is a strong indicator of a failed or removed filter.
5. Perform a forced regeneration with the scan tool and watch exhaust temperature before and after the DPF (should reach 550-650 °C) and the pressure drop; if the pressure does not rise during the drive before regeneration and does not fall after, the filter is not trapping soot.
6. If the filter is confirmed damaged, replace it with an OE-quality unit, reset the ash load / DPF adaptation values in the ECU, and address the root cause (oil consumption, injector leak, EGR/turbo faults, failing temperature sensors) or the new filter will fail the same way.

Symptoms linked to this code

• Black smoke from the exhaust
• Loss of power when accelerating
• DPF warning light on

Terms to know

Related codes

Nearby codes in this group

• P2001NOx Trap Efficiency Below Threshold
• P2003Particulate Trap Efficiency Below Threshold
• P2000NOx Trap Efficiency Below Threshold
• P2004Intake Manifold Runner Control Stuck Open (Bank 1)
• P2005Intake Manifold Runner Control Stuck Open
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• P2007Intake Manifold Runner Control Stuck Closed
• P2008Intake Manifold Runner Control Circuit/Open