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P04A8 Powertrain

Exhaust Pressure Control Valve B Position Sensor Circuit Low

Same as P04A6 with the signal voltage below the plausible range. 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

  • Exhaust pressure position sensor b

Common causes

  • High likelihood: Signal 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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