P20EE — SCR NOx Catalyst Efficiency Below Threshold Bank 1 Catalyst 1

P20EE: SCR NOx Catalyst Efficiency Below Threshold Bank 1 Catalyst 1 — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

SCR NOx Catalyst Efficiency Below Threshold Bank 1 Catalyst 1. Basic catalogue definition; diagnostic details have not yet been reviewed.

Affected system: Powertrain

Symptoms

  • An engine or exhaust-treatment warning may illuminate.
  • Some vehicles may enter an emissions-related reduced-power mode.

Possible causes

  • Incorrect or insufficient reductant dosing, contaminated DEF, or a failing NOx sensor can affect the SCR assessment.
  • An exhaust leak, related wiring fault or ineffective SCR catalyst is also possible.

What to check

  • Check DEF level and condition and retrieve related SCR or NOx-sensor faults.
  • Inspect reductant injection, exhaust connections, sensor wiring and available live measurements.
  • Evaluate catalyst performance only after dosing and sensor problems have been excluded.

Also written as: P20EE-00, P20EE00 (some scan tools add the fault-type byte, e.g. -00).