P2003 - Diesel Particulate Filter Efficiency Below Threshold (Bank 1)
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System
Powertrain (Engine & Gearbox)
OBS!This code is in a manufacturer-specific range. The description may vary depending on the vehicle manufacturer.
Related Fault Codes
Technical Description
P2003 is a generic diagnostic trouble code indicating that the Diesel Particulate Filter (DPF) efficiency has fallen below the minimum threshold on Bank 1. The Engine Control Unit (ECU) monitors the DPF performance using differential pressure sensors to evaluate the soot accumulation and flow characteristics. If the pressure delta is outside the expected range (e.g., too low indicating a cracked substrate, or failing to decrease after a regeneration cycle), the code triggers. The ECU integrates data from the Mass Air Flow (MAF) sensor and Exhaust Gas Temperature (EGT) sensors via the CAN bus to validate filter performance.
Possible Causes
Faulty or cracked Diesel Particulate Filter (DPF)
Exhaust leak upstream of or near the DPF
Faulty DPF differential pressure sensor or damaged pressure hoses
Faulty Mass Air Flow (MAF) sensor providing incorrect flow data for calculations
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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