P0720: Output Shaft Speed Sensor Circuit
What to do
Expect a fixed gear, and possibly a dead speedometer and several warning lights at once. That combination points at one shared sensor rather than at multiple failures. Drive it home rather than on — the converter stays unlocked in the protective mode, which heats the fluid.
What this code means
The sensor reporting the speed of the transmission's output shaft is not sending a usable signal. Together with the turbine speed sensor at the other end of the gearbox, it gives the module the two numbers whose ratio tells it which gear is actually engaged — so losing it disables the transmission's ability to check its own work, and it defaults to a fixed gear.
What makes this code recognisable from the driver's seat is how much else reads the same signal. On many vehicles the output speed sensor is the vehicle speed source, feeding the speedometer, cruise control, stability control and speed-sensitive steering. So a dead speedometer arriving at the same moment as a transmission that stopped shifting, with two or three other warning lights for good measure, is not several faults. It is one sensor, and the breadth of the symptoms is the clue rather than the alarm.
Likely causes
Start here
- Faulty output speed sensor · moderate
- Damaged transmission wiring harness · moderate
- Corroded transmission connector · moderate
Less common
- Metal debris on the sensor tip · specialist
- Damaged reluctor or tone ring · specialist
Rare
- Faulty transmission control module · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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