Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer is having trouble reading the speed of the part that connects the engine to the wheels. It's like if your bicycle's speedometer wasn't working right.
The P0721 code indicates that the transmission control module (TCM) is detecting an issue with the output shaft speed sensor's signal, which is outside the expected range or performance levels.
The output shaft speed sensor measures the rotational speed of the transmission's output shaft. This data is used by the TCM to control shifting and other transmission functions. When the sensor's signal is erratic or outside the expected range, the P0721 code is triggered.
• Erratic or harsh shifting
• Speedometer malfunctions
• Check Engine Light illuminated
• Faulty output shaft speed sensor
• Damaged or corroded wiring and connectors
• Malfunctioning transmission control module (TCM)
TCM: Transmission Control Module
OBD-II: On-Board Diagnostics, Second Generation
• Use an OBD-II scanner to verify the code.
• Inspect the output shaft speed sensor and its wiring for damage.
• Test the sensor's resistance and signal output.
• Replace the output shaft speed sensor if faulty.
• Repair or replace damaged wiring and connectors.
• Reprogram or replace the TCM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Ford F-150
• Chevrolet Silverado
• Honda Accord
• Regularly inspect and maintain transmission components.
• Ensure wiring and connectors are free from corrosion.
• Update vehicle software as recommended by the manufacturer.
Sensor Issue
• Avoid driving at high speeds until the issue is resolved.
• Consult a professional mechanic for a thorough diagnosis.
Check if your vehicle's powertrain warranty covers sensor replacements.
The P0721 code has been a common issue in vehicles with electronic transmissions, especially as they age.
Moderate – It should be addressed soon to prevent further transmission issues.
Ignoring this code could lead to unsafe driving conditions due to erratic shifting.
• Vehicle at operating temperature
• Driving at various speeds
The output shaft speed sensor is typically located on the transmission near the output shaft.
Q: Can I drive with a P0721 code?
A: It's not recommended to drive for long periods with this code, as it can cause further transmission damage.
Q: How do I reset the P0721 code?
A: After repairs, use an OBD-II scanner to clear the code. If the issue is resolved, it should not return.
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