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P25B7 Powertrain

Auxiliary Ignition Switch On/Start Position Circuit

General electrical fault on the auxiliary ignition switch On/Start input. Used on commercial vehicles or upfit applications where a second ignition switch (in a sleeper cab, work platform or crew compartment) can crank the engine.

Affected components

  • Auxiliary ignition switch
  • Wiring harness

Common causes

  • High likelihood: Open or shorted wire

Diagnostic notes

  • The malfunction indicator lamp may illuminate

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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