Output Speed Sensor Range/Performance
The P0721 code indicates that the Powertrain Control Module (PCM) has detected an output speed sensor signal that is out of the expected range or not performing correctly. The output speed sensor monitors the rotational speed of the transmission output shaft, which is used for shift timing, torque converter clutch control, and speedometer operation. A faulty sensor, wiring issues, or mechanical problems within the transmission can cause this code.
01. Most Common Causes
- Faulty output speed sensor
- Damaged or corroded wiring/connectors
- Metal debris or contamination on the sensor
- Internal transmission mechanical failure
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Erratic or inaccurate speedometer readings
- Harsh or delayed shifting
- Transmission may go into limp mode
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the output speed sensor and wiring for damage or corrosion.
Step 3: Test sensor resistance and AC voltage output while rotating the wheels.
Step 4: Check for metal debris on the sensor magnet; clean or replace as needed.
Step 5: If sensor and wiring are good, inspect transmission for mechanical issues.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can cause transmission damage or unsafe driving conditions due to erratic shifting or speedometer failure.
How much does it cost to fix?▼
Typically $50-$150 for a sensor replacement, but costs can be higher if wiring repairs or transmission work is needed.