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P05F4 Powertrain

Exhaust Aftertreatment Power Relay Control Circuit Low

Same as P05F3 with the control line shorted to ground. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.

Affected components

  • Aftertreatment power relay

Common causes

  • High likelihood: Control line shorted to ground
  • Low likelihood: Connector pins corroded - high contact resistance
  • Low likelihood: Harness chafing through insulation

Diagnostic notes

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

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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