OBD-II code · Powertrain (generic)
P0721 Output Speed Sensor Circuit Range/Performance
The transmission output speed sensor signal is implausible compared to vehicle speed and gear ratio. Sometimes set together with VSS or input-speed-sensor codes.
Is it safe to drive with P0721?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyOutput speed sensor failed
- Less likelySensor element aged beyond calibration window
- Less likelySensor mounting loose - signal damping
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
- 1–4 h
- Emissions test
- Usually unaffected
- Parts involved
- Transmission Output Speed Sensor, Sensor Wiring
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.