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P25B8 Powertrain

Auxiliary Ignition Switch On/Start Position Circuit Low

Auxiliary ignition switch On/Start input reads stuck low — short to ground or stuck-closed contact. 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

  • Auxiliary ignition switch
  • Wiring harness

Common causes

  • High likelihood: Wire 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

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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