P2002: Particulate Trap Bank 1 Efficiency Below Threshold

What it means

The control module has detected particulate trap efficiency below the expected threshold on bank 1. This code does not by itself establish whether the filter is loaded, damaged, or affected by a sensor or leak.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

The diesel particulate filter (DPF), also called the particulate trap, captures soot in the exhaust from bank 1. The control module compares the filter’s measured performance with expected values, including pressure readings across it; P2002 sets when bank 1’s trap appears less effective than expected, but does not identify whether the filter itself or a leak or sensor is responsible.

Common causes

Most likely first.

1. DPF heavily loaded — repeated short trips prevent regeneration
2. Filter substrate cracked or melted from runaway regeneration
3. Differential pressure sensor drift
4. Leak around DPF housing

Symptoms

• Check engine light or DPF warning light on
• Power loss / limp mode
• Increased fuel consumption
• Failed forced regeneration attempts

How to diagnose it

1. Use a scan tool to record freeze-frame data and compare bank 1 DPF pressure and soot-loading readings with the manufacturer's specification before attempting regeneration.
2. Inspect the DPF housing, joints, and nearby exhaust for soot traces or other signs of a leak that could distort pressure measurements.
3. Check the differential-pressure sensor and its hoses for damage, blockage, disconnection, or contamination, and compare its readings with the manufacturer's specification.
4. If the sensor and exhaust path check out, assess soot loading and regeneration history to determine whether repeated short trips have prevented regeneration.
5. If loading is not the explanation or regeneration repeatedly fails, have the filter substrate assessed for cracking or melting before replacing the DPF.

Common fixes

• Repair an exhaust leak at the DPF housing or its joints.
• Reconnect or replace damaged or blocked differential-pressure sensor hoses.
• Repair wiring or replace a differential-pressure sensor that fails checks against the manufacturer's specification.
• Perform the vehicle's prescribed regeneration if the filter is loaded and conditions allow it.
• Replace a cracked or melted DPF after confirming the substrate is damaged.

Can I keep driving?

If power is normal and no DPF warning is demanding immediate service, drive gently and arrange diagnosis soon; avoid repeated short trips and heavy loads. With limp mode, substantial power loss, or failed regeneration attempts, stop relying on the vehicle for routine driving, since continued soot accumulation can further restrict the exhaust.