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P077C Powertrain

Output Shaft Speed Sensor Circuit Low

Output shaft speed sensor signal voltage below the lower limit — short to ground or open supply. TCM disables vehicle-speed dependent shift logic and may force limp-home.

Affected components

  • Output shaft speed sensor
  • Sensor wiring

Common causes

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

Possible symptoms

  • Check engine or transmission warning light on
  • Harsh, delayed, or missing shifts
  • Possible limp mode (locked in one gear)
  • Slipping or shuddering during gear changes

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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