P0720
UniversalOutput Speed Sensor Circuit Malfunction
Medium SeverityThe P0720 code indicates a problem with the Output Speed Sensor circuit. This sensor measures the rotational speed of the transmission's output shaft, and a malfunction here can lead to incorrect speedometer readings or erratic transmission shifting.
⚠️ Before You Begin (Safety First)
Always ensure the vehicle is safely supported on jack stands if working underneath. Disconnect the battery before performing any electrical work to prevent accidental shorts or injury. Allow exhaust and engine components to cool down before touching them.
Common Symptoms
- Check Engine Light illuminated
- Erratic or harsh transmission shifting
- Speedometer not working or inaccurate
- Transmission may enter 'limp mode'
- Poor fuel economy
Common Causes
- Faulty Output Speed Sensor
- Damaged wiring or connectors in the sensor circuit
- Short circuit or open circuit in the sensor wiring
- Debris or metallic particles on the sensor tip
- Faulty Transmission Control Module (TCM) or Powertrain Control Module (PCM) (less common)
Frequently reported on: General/Universal
Diagnostic Steps
- Locate the Output Speed Sensor on the transmission (consult a repair manual for exact location).
- Inspect the sensor and its wiring harness for any visible damage, corrosion, or loose connections.
- If possible, test the sensor's resistance with a multimeter (refer to service specifications).
- Clean any debris or metallic shavings from the sensor's tip.
- If the sensor is faulty, carefully remove and replace it, ensuring proper installation and connection.
👨🔧 When to Call a Professional
If you've replaced the Output Speed Sensor and the code persists, or if you suspect internal transmission problems, it's best to consult a professional mechanic. Diagnostic procedures for transmission issues can be complex and may require specialized tools.
Commonly Asked Questions
What does the Output Speed Sensor do?
The Output Speed Sensor measures the speed of the transmission's output shaft, providing crucial data to the vehicle's computer for accurate speedometer readings and proper transmission shifting.
Can I drive with a P0720 code?
While you might be able to drive, it is not recommended for long periods. An inaccurate speedometer and erratic shifting can be dangerous and potentially lead to further transmission damage.
Is the Output Speed Sensor the same as the Vehicle Speed Sensor (VSS)?
Not always. While they both measure speed, the VSS typically measures overall vehicle speed (often at the transmission or wheel), and the Output Speed Sensor specifically measures the transmission's output shaft speed. They can sometimes be integrated or perform similar functions.
How do I test the Output Speed Sensor?
You can typically test the sensor's resistance using a multimeter, comparing the readings to factory specifications. Some sensors can also be tested by monitoring their voltage output while the wheel is spun, though this is more advanced.
What if replacing the sensor doesn't fix P0720?
If replacing the sensor doesn't resolve the code, the issue likely lies with the wiring harness (damaged wires, poor connections) or, less commonly, a faulty Transmission Control Module (TCM) or Powertrain Control Module (PCM). A professional diagnosis would be recommended.