OBD-II Code · Powertrain
P0721
Output Speed Sensor Performance
Severity
high
Left alone, this one tends to take other parts with it.
Can you drive it
Not for long
Driving on this one risks further damage. Get it to a shop rather than carrying on with it.
Indicative cost (USD)
$200–$1,800
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Output speed sensor signal is implausible.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Speedometer erratic
- Harsh shifts
- Limp mode
Likely causes
- Failed output speed sensorMost common
- Wiring
- Bad tone ring inside trans
Look up another code
P0721 — frequently asked
What does a P0721 code mean?
Output speed sensor signal is implausible.
What causes a P0721 code?
Common causes: Failed output speed sensor; Wiring; Bad tone ring inside trans.
What are the symptoms of a P0721 code?
Typical symptoms: Speedometer erratic; Harsh shifts; Limp mode.
Is it safe to drive with a P0721 code?
Not for long. Driving on this one risks further damage. Get it to a shop rather than carrying on with it. Estimated repair: $200-$1,800.
How do I diagnose a P0721 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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