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.

No — this code can cause damage if you keep driving. Get it diagnosed before continuing. Estimated repair: $200-$1,800.

OBD-II Code · Powertrain

Output Speed Sensor Performance

high severityDo not drive$200-$1,800

Output speed sensor signal is implausible.

Common symptoms

Likely causes

Where to start

Try the cheapest cause first. Start by checking: failed output speed sensor.
Cost & scope. $200-$1,800
If the code returns after the fix: escalate to a shop or scanner with live-data and freeze-frame. A code that re-sets means the underlying fault is still there. Don't keep driving with this one active — risk of damage.

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