P077C — Output Shaft Speed Sensor Circuit Low

P077C: Output Shaft Speed Sensor Circuit Low — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

Output Shaft Speed Sensor Circuit Low. Basic catalogue definition; diagnostic details have not yet been reviewed.

Affected system: Powertrain

Symptoms

  • Warning light may illuminate
  • Related system function may be impaired
  • Vehicle-specific symptoms vary

Possible causes

  • Implausible sensor or switch signal, poor ground, connector corrosion, or wiring damage
  • Related wiring, connector, power or ground fault
  • Vehicle-specific mechanical or control issue

What to check

  • Record stored and pending codes and freeze-frame data
  • Compare the named sensor or switch signal with actual operating conditions; inspect the connector, reference supply, ground and harness.
  • Confirm measured values against the vehicle service information
  • Retest under the conditions that set the code
  • Compare the named sensor or switch signal with actual operating conditions; inspect the connector, reference supply, ground and harness.
  • Repair the verified cause and confirm the code does not return

Also written as: P077C-00, P077C00, PO77C (some scan tools add the fault-type byte, e.g. -00).