Error code

OBD2 P0721

OBD2P0721
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Output Speed Sensor Circuit Range/Performance.

Severity

highCan be driven but may experience erratic gear shifts, increased fuel consumption, and other issues. Not recommended for extended driving.

Summary

P0721 indicates an issue with the transmission output shaft speed (OSS) sensor circuit range or performance on automatic transmissions. This sensor provides critical data to the PCM/TCM for gear shift control.

Symptoms

  • Illuminated warning light
  • Erratic or harsh gear shifts
  • Transmission may fail to engage gears or be stuck in one gear
  • Increased fuel consumption
  • Engine misfire-like symptoms
  • Speedometer inaccuracies

Common Causes

  • Damaged, burnt, shorted, disconnected, or corroded wiring and connectors
  • Defective transmission output shaft speed sensor
  • Low or contaminated transmission fluid levels
  • Failed PCM/TCM (rare)

Diagnosis

  1. Check transmission fluid level and condition
  2. Inspect wiring and connectors for damage or corrosion
  3. Perform electrical tests on the sensor circuit
  4. Test the output shaft speed sensor itself

Fixes

  • Replace defective transmission output shaft speed sensor if necessary

FAQ

What should I do if my car has P0721?

First, check the transmission fluid level and condition. Then inspect wiring and connectors for damage or corrosion. If issues persist, consult a professional mechanic.

Is it safe to drive with P0721?

Driving is possible but not recommended due to potential erratic gear shifts and increased fuel consumption.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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