Error code

OBD2 P2001

OBD2P2001
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

NOx Trap Efficiency Below Threshold.

Severity

moderateThe vehicle can be driven, but performance issues and potential emissions violations may occur.

Summary

The P2001 code indicates that the NOx trap efficiency is below threshold on bank 2 of the diesel engine. This means the system designed to reduce nitrogen oxide emissions is not functioning properly.

Symptoms

  • Excessive smoke from the exhaust
  • Reduced overall engine performance
  • Hotter than normal engine temperatures
  • Decreased fuel efficiency
  • Erratic transmission shift patterns due to reduced engine RPM capacity
  • Illumination of the service engine soon/check engine lamp

Common Causes

  • A defective or overloaded NOx trap or NOx trap element
  • Malfunction in the diesel exhaust fluid injection system
  • Inadequate NOx reductant fluid
  • Inoperable exhaust gas recirculation (EGR) system
  • Severe exhaust leak upstream of the NOx trap

Diagnosis

  1. Inspect all system wiring and connectors for defects.
  2. Check the SCR and exhaust system for obvious defects and make repairs as needed.
  3. Ensure there is adequate reductant in the diesel exhaust fluid reservoir.
  4. Test EGR operation using a scanner; repair any related codes before diagnosing P2001.
  5. Use a scanner to retrieve stored trouble codes and freeze frame data, then clear them and test drive the vehicle.
  6. Narrow down the data stream to observe NOx sensors' output voltages.

Fixes

  • Replace the defective or overloaded NOx trap element.

FAQ

What is a NOx trap?

A NOx trap, also known as an adsorption system, uses materials like zeolite to capture and reduce nitrogen oxide emissions from diesel engines.

How do I know if my NOx reductant fluid level is low?

Check the reservoir for the diesel exhaust fluid (DEF) to ensure it has an adequate amount of reductant fluid.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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