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P209A Powertrain

Reductant Injection Air Pressure Sensor B Circuit

A general electrical fault is reported on reductant injection air-pressure sensor B — the second air-assist pressure sensor on dual-bank or dual-injector DEF systems.

Affected components

  • Reductant air pressure sensor

Common causes

  • High likelihood: Sensor failed
  • Medium likelihood: Harness fault

Possible symptoms

  • Check engine light or NOx warning on
  • AdBlue/DEF level or quality warning
  • Possible no-start countdown after ignore period
  • Failed emissions inspection (NOx)

Diagnostic notes

  • The malfunction indicator lamp may illuminate
  • This code can affect emissions

Related codes

Sources

Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.

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