Transmission · Powertrain · generic (SAE-defined)
P0720: Output Speed Sensor Circuit
P0720 means the computer detected an electrical problem with the transmission output speed sensor (OSS), which measures how fast the output shaft and driveline are turning.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0720 sets
The output speed sensor (OSS) reads a toothed ring on the transmission output shaft or park gear. The transmission control module (TCM) or powertrain control module (PCM) uses the signal for shift timing, slip calculations and often vehicle speed. If the circuit is open, shorted or electrically out of range, the module sets P0720. Details vary by manufacturer.
Common causes of P0720
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Failed output speed sensor
- Damaged wiring or corroded connector
- Metal debris on the sensor tip
- Damaged tone ring or reluctor
- Low or contaminated transmission fluid
- TCM or PCM fault
P0720 symptoms
- Check engine light on
- Speedometer erratic or not working
- Harsh or incorrect shifting, or limp mode
- Cruise control not working
- ABS or traction control warning on some vehicles
How P0720 is diagnosed
- Record freeze frame data and all codes, including ABS and vehicle speed codes
- Compare output speed with wheel speed sensor data during a road test
- Inspect the sensor connector and wiring near the transmission tail
- Test sensor resistance or signal output per factory procedure
- Remove the sensor and check for debris or damage
- Check the circuit for opens and shorts back to the module
Typical fixes for P0720
- Replace the output speed sensor
- Repair wiring or connector faults
- Clean debris and service the transmission fluid
- Repair a damaged reluctor
- Replace or reprogram the control module if it is faulty
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P0720 FAQ
What does code P0720 mean?
P0720 means the computer detected an electrical problem with the transmission output speed sensor (OSS), which measures how fast the output shaft and driveline are turning. The standard definition is "Output Speed Sensor Circuit."
Can I drive with a P0720 code?
Drive only briefly and carefully. Losing output speed can upset shifting, cruise control and the speedometer, and the transmission may drop into limp mode.
Why did my speedometer stop working with P0720?
On many vehicles the output speed sensor provides the vehicle speed signal used by the speedometer, so a failed sensor or circuit can freeze or drop the reading.
Is P0720 related to P0500?
Often. P0500 is a vehicle speed sensor code, and on vehicles where the output speed sensor supplies vehicle speed, both codes can set from the same fault.
Keep researching
More transmission codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.