Code result
P077B
Output Shaft Speed Sensor Circuit - Direction Error
High severity
What it means
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.
Is it safe to drive?
No — stop driving
This code points to a problem that can cause damage or affect safety. Avoid driving and have the vehicle diagnosed promptly.
Most likely causes
Sensor wiring swapped after service
highOne of the most commonly reported causes for this code — check this first.
Wrong sensor part installed
mediumA plausible cause — test and verify before replacing parts.
Related help
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