P0720: Output Speed Sensor Circuit
The transmission control unit has detected a fault in the output speed sensor circuit.
Normal risk
Usually drivable, but shifting may be harsh or the gearbox may stay in one gear. Have it checked soon.
Short answer · Can I keep driving with P0720?
Usually yes, at moderate speed. The gearbox may shift harshly or stay in a fixed gear, and the speedometer may stop working. Have it checked soon.
What does P0720 mean?
P0720 means the signal from the sensor on the transmission output shaft is missing, erratic or does not fit the input speed and engaged gear. On many cars this sensor also supplies vehicle speed. A failed sensor, metal debris on its tip, damaged wiring or a corroded connector are typical causes.
What the car does when the code is set
The check engine light comes on. The speedometer may stop working, cruise control is usually disabled and an automatic gearbox may shift harshly or stay in a fixed gear. ABS or stability warnings may also appear.
How the system works
The vehicle speed signal comes from a sensor on the gearbox or, on most modern cars, from the wheel speed sensors through the ABS module. The engine and gearbox control units, speedometer, cruise control and other systems use it. Code P0500 means the signal is missing, implausible or does not match what other inputs suggest.
Common symptoms
Possible causes
Listed without ranking. The cause on your car depends on make, engine and mileage — see the maker notes below.
- Faulty output speed sensorThe sensor that reads the gearbox output shaft has failed or is covered with metal particles.
- Faulty speed sensorThe sensor can fail or be damaged by dirt and metal particles.
- Wiring or connector faultDamaged, corroded or loose wiring interrupts the speed signal.
- Damaged sensor ring or driveA cracked or dirty tone ring or a worn drive gear gives no or irregular signals.
- ABS module or network faultOn many cars the vehicle speed comes from the ABS system over the network.
- Instrument cluster faultLess common, but some cars route the speed signal through the cluster.
How it is diagnosed
- Check the speedometerA speedometer that does not work or jumps points to the speed signal itself.
- Read codes from all modulesABS or wheel speed codes often show where the problem starts.
- Inspect the sensor and wiringLook for damage, dirt and loose connectors at the sensor.
- Check the signal with a scan toolA workshop compares the vehicle speed signal with wheel speeds while driving.Do not test-drive with faulty speed signals on busy roads; cruise control, gear shifts and ABS may not work normally.
Questions about P0720
Does P0720 affect the speedometer?
On cars that take vehicle speed from the gearbox, yes. On cars that use wheel speed sensors, the speedometer usually keeps working.
Why does my automatic shift badly with this code?
The gearbox uses vehicle speed to choose shift points. Without a valid signal it may shift harshly or stay in one gear.