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P2AA2

Alternative Fuel Return Line Insufficient Flow

The AFCM detects that the flow through the alternative fuel return line is below the expected minimum for the active operating mode. Restricted line, stuck valve, or pump output too low.

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

Common causes

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

  • Return line restricted by debrisCommon
  • Return line valve stuck closedPossible

Parts involved

  • Alt Fuel Return Line
  • Alt Fuel Return Line Valve
  • Alt Fuel Pump

P2AA2 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.