P077B
Output Shaft Speed Sensor Circuit - Direction Error
The TCM reads a direction from the output shaft speed sensor that contradicts the commanded gear — for example reverse direction while drive is engaged, or forward direction while reverse is engaged. Either the sensor wiring is swapped, the sensor is wrong, or the gear actually engaged is not the one commanded.
The TCM reads a direction from the output shaft speed sensor that contradicts the commanded gear — for example reverse direction while drive is engaged, or forward direction while reverse is engaged. Either the sensor wiring is swapped, the sensor is wrong, or the gear actually engaged is not the one commanded.
Common causes
- high
Sensor wiring swapped after service
One of the most commonly reported causes for this code — check this first.
Typical part cost: $220-1100
- medium
Wrong sensor part installed
A plausible cause — test and verify before replacing parts.
Typical part cost: $220-1100
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First things to check
- 1Confirm the code with a scan tool and check for additional related codes.
- 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.
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Related codes
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Frequently asked questions
What does P077B mean?
P077B means "Output Shaft Speed Sensor Circuit - Direction Error". It is a generic OBD-II code that points to a fault in the transmission.
What are the most common causes of P077B?
sensor wiring swapped after service; wrong sensor part installed — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.
Can I keep driving with this code?
This code points to a problem that can cause damage or affect safety. Avoid driving and have the vehicle diagnosed promptly. Use the Wrenchify app for a full diagnosis specific to your vehicle.
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