OBD II Fault Code

  • OBD II P077A

OBD-II Code Transmission may not shift properly is defined as a Output Speed Sensor Circuit - Loss of Direction Signal

The Output Speed Sensor tells the Transmission Control Module (TCM) how fast the output shaft of the transmission is spinning so it can verify the correct gear is engaged. Some manufacturers add a second Output Shaft Speed Sensor to enable the TCM to determine what direction the shaft is rotating. When the TCM receives an implausible signal from these sensors, the engine control module (PCM) or Hybrid Control Module will set code P077A.

Transmission may not shift properly Symptoms

  • Increased fuel consumption
  • Transmission may not shift properly

Common Problems That Trigger the P077A Code

  • High voltage control module failure
  • Output shaft speed sensor failure
  • Transmission Control Module (TCM) failure
  • Wiring issue
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