Code Definition

P077C — Output Speed Sensor Circuit Low

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Toyota

About P077C

P077C is a generic (obd-ii standard) powertrain diagnostic trouble code recorded for Toyota vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P077C is stored, the module has detected a signal or supply voltage lower than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P077C is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The output speed sensor measures how fast the transmission output shaft is turning and is the module's reference for road speed, gear ratio calculation, shift scheduling, and torque converter lockup control. On most transmissions it is a variable reluctance sensor generating its own alternating current signal from a toothed rotor on the output shaft, although hall effect designs supplied with a reference voltage are also common. DTC P077C sets when the control module detects the output speed sensor signal circuit sitting at an abnormally low voltage, which normally indicates a short to ground,...

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