OBD-II code · Powertrain (generic)
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.
Is it safe to drive with P077B?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySensor wiring swapped after service
- PossibleWrong sensor part installed
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.6–3 h
- Emissions test
- Usually unaffected
- Parts involved
- Output Shaft Speed Sensor, Transmission
Related codes
- P077AOutput Shaft Speed Sensor Circuit - Loss of Direction Signal
- P0778Pressure Control Solenoid B Electrical
- P0779Pressure Control Solenoid B Intermittent
- P077COutput Shaft Speed Sensor Circuit Low
- P077DOutput Shaft Speed Sensor Circuit High
- P077ETransmission Fluid Temperature Measurement System - Multiple Sensor Correlation
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.