Code Definition

P2001 — NOx Trap Efficiency Below Threshold - Bank 2

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P2001

P2001 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P2001 is stored, the module has detected a signal or supply voltage lower than the expected operating range; and a bank-specific fault, meaning it applies only to one cylinder bank of a multi-bank engine.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P2001 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The Engine Control Module (ECM) monitors the efficiency of the NOx (nitrogen oxide) storage and reduction trap on Bank 2 by comparing readings from the upstream and downstream NOx sensors. DTC P2001 is set when the measured NOx reduction across the Bank 2 trap falls below the manufacturer calibrated threshold during a monitor cycle, indicating that the trap is no longer storing or converting NOx effectively. The NOx trap collects nitrogen oxides during normal lean engine operation and is periodically regenerated by brief rich fuel commands from the ECM, which release and reduce the stored NOx ...

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