OBD-II code · Powertrain (generic)
P077C Output Shaft Speed Sensor Circuit Low
Output shaft speed sensor signal voltage below the lower limit — short to ground or open supply. TCM disables vehicle-speed dependent shift logic and may force limp-home.
Is it safe to drive with P077C?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySignal wire shorted to ground
- Less likelyConnector pins corroded - high contact resistance
- Less likelyHarness chafing through insulation
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
- 0.5–2 h
- Emissions test
- Usually unaffected
- Parts involved
- Output Shaft Speed Sensor, Sensor Wiring
Related codes
- P0779Pressure Control Solenoid B Intermittent
- P077AOutput Shaft Speed Sensor Circuit - Loss of Direction Signal
- P077BOutput Shaft Speed Sensor Circuit - Direction Error
- P077DOutput Shaft Speed Sensor Circuit High
- P077ETransmission Fluid Temperature Measurement System - Multiple Sensor Correlation
- P077FReverse 2 Incorrect Ratio
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.