P0720
Output Shaft Speed Sensor Circuit
Transmission
Generic OBD-II
High
What it means
P0720 means the transmission's output shaft speed sensor circuit has a fault. This sensor measures how fast the output shaft turns, which the TCM uses for shift timing, torque-converter lockup, and often the speedometer. A bad signal causes harsh or erratic shifting, a wrong speedometer reading, or a protective limp mode. It points at the sensor or its wiring rather than at the engine's ability to start.
High
Can I keep driving? The transmission may shift harshly or drop into limp mode, and the speedometer can read wrong — driveable slowly, but get it fixed soon.
Common symptoms
What you'll notice
- Check-engine light on (sometimes a transmission warning light)
- Harsh, erratic, or delayed shifting
- Speedometer reading incorrectly or dropping out
- Limp mode locking the transmission in one gear
Common causes
Most likely first
- Faulty output shaft speed sensorLikely
- Damaged wiring or a corroded connector at the sensorCommon
- Debris on the sensor tip or a damaged reluctor/tone ringCommon
- Low or degraded transmission fluid affecting the signal; less commonly a failed TCMLess often
How to diagnose & fix
Work through it in order
- Scan and record freeze-frame data, and compare input vs. output speed readings to confirm the output sensor is at fault.
- Inspect the sensor's connector and wiring for damage or corrosion; clean the sensor tip if accessible.
- Check the transmission fluid level and condition.
- Replace the output shaft speed sensor if its signal stays faulty with good wiring; consider the TCM only after the sensor and harness are ruled out.
FAQ
Quick answers
Is it safe to drive with P0720?+
Short, slow trips may be fine, but limp mode and harsh shifts can strain the transmission, and a wrong speedometer is a safety concern. Have it diagnosed soon.
Can I just clear P0720?+
It clears, but returns once the sensor signal faults again. Repair the sensor or wiring first.
Related codes
Often seen with P0720
Read & clear P0720 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX