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P04A1

Exhaust Pressure Control Valve B Low

Same as P049F with the control line shorted to ground.

  • Check engine light: Yes
  • Emissions related: Yes
  • Repair difficulty: medium

Common causes

Ordered by how often each turns out to be the cause.

  • Control line shorted to groundCommon

Parts involved

  • Exhaust Pressure Valve B

P04A1 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.