P077DOutput Shaft Speed Sensor Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- GM's transmission modules from 2019 to 2025 (9- and 10-speeds) also read the active output speed sensor's line voltage as an analog value. P077D is the mirror of P077C: the voltage is above 4.75 V – a short to the module supply of under about 0.5 Ω – for more than 0.05 s, after one trip. GM then blocks the no-signal and ratio checks; a GM hybrid also blocks its idle diagnosis. Without usable output speed the transmission enters limp mode, and speedometer or cruise control may fail.
- What you may notice
- Check engine light at once (GM)
- Limp mode
- Speedometer or cruise control failed
- Shift problems
- Likely causes
- LikelySignal wire shorted to sensor supply or battery voltage
- PossibleSensor faulty internally
- PossibleGround fault at the sensor, corroded connector
- RareModule input
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €120 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.