All codes
P0721Transmission Issues
Output Speed Sensor Circuit Range/Performance
P0721 means the output shaft speed signal does not agree with expected transmission or vehicle operation. Learn what to check before replacing parts.
What you may notice
Symptoms
- 01Warning light may illuminate
- 02Intermittent or implausible scan data
- 03Vehicle-specific symptoms may vary
Where to look first
Common causes
- 01An intermittent speed sensor, damaged wiring, or an internal transmission issue can make the speed signal implausible.
- 02Wiring, connector, or ground fault
- 03Vehicle-specific mechanical or control issue
A sensible sequence
Best diagnostic order
- 01Save codes and freeze-frame information
- 02Compare output speed with vehicle speed and gear data while checking connector condition and related transmission codes.
- 03Confirm readings with vehicle-specific specifications
- 04Verify the repair under the conditions that set the code
Step by step
What to check and repair
- 01Compare output speed with vehicle speed and gear data while checking connector condition and related transmission codes.
- 02Repair only the verified cause and retest
Read the signals
Live-data clues
Related sensor or switch signal
- Typical behavior
- Plausible and consistent with the operating condition
- Possible clue
- An unexpected value or dropout helps localize the fault
| Parameter | Typical behavior | What it can suggest |
|---|---|---|
| Related sensor or switch signal | Plausible and consistent with the operating condition | An unexpected value or dropout helps localize the fault |
What P0721 means
The output shaft speed signal does not agree with expected transmission or vehicle operation. The code identifies an observed condition; it does not prove which part needs replacement.
Diagnostic direction
Compare output speed with vehicle speed and gear data while checking connector condition and related transmission codes.
Before clearing the code
Save stored and pending codes and freeze-frame data. Use service information for the exact vehicle before repair, then confirm the issue no longer returns.