P0720: Output Speed Sensor Circuit Malfunction

What does P0720 mean?

The P0720 diagnostic trouble code (DTC) means there is a problem with the output speed sensor circuit. This code is triggered when the engine control module or transmission control module detects an irregular signal from the output speed sensor. The output speed sensor monitors the rotational speed of the transmission’s output shaft and uses this data to control shift timing for the transmission and calculate the vehicle's speed.

The importance of addressing P0720

The output speed sensor is crucial in transmission operation and vehicle performance. If the sensor provides bad data (or no data), the transmission can shift erratically or harshly and make driving your car smoothly more difficult. Incorrect speed readings can also cause issues with the speedometer, cruise control and the anti-lock braking system (ABS). If left unaddressed, this issue could lead to transmission damage or failure.

Is my car safe to drive with this code?

Driving with the P0720 code is risky, especially if the transmission begins shifting erratically or the speedometer stops functioning. While the vehicle may still operate, inaccurate speed data can make a car less safe to drive. If symptoms are severe, such as transmission slippage, rough shifts, or a failure to shift at all, it's best to avoid driving until repairs are made.

Common symptoms of the P0720 error code

• The check engine light is on

• Erratic or harsh shifts

• Speedometer not working

• Hesitation or stalling when accelerating

• Decreased fuel efficiency

• Cruise control failure

How is error code P0720 diagnosed?

Diagnosing the P0720 code typically involves the following steps:

• Retrieve the code: Use an OBD-II scanner to confirm the P0720 code and check for related transmission codes.

• Inspect the output speed sensor: Check for physical damage, corrosion or loose connections on the sensor.

• Examine wiring and connectors: Inspect the sensor’s wiring harness for frayed wires, poor grounding or loose connections.

• Test the sensor: Use a multimeter to measure the resistance and voltage output of the speed sensor.

• Check the transmission fluid: Verify that the transmission fluid level and quality are within manufacturer specifications.

• Evaluate the engine control module/transmission control module: If the sensor and wiring are in good condition, test the engine control module or transmission control module for faults.

How is error code P0720 fixed?

Repairs for the P0720 code may include:

• Replacing a faulty output speed sensor.

• Repairing or replacing damaged wiring or connectors in the sensor circuit.

• Cleaning the speed sensor and surrounding area to remove dirt or debris.

• Flushing and replacing contaminated or low transmission fluid.

• Replacing a malfunctioning engine control module or transmission control module if necessary.

Related reading

Follow the link below to reach our diagnostic check engine trouble codes catalog:
On-board diagnostics (OBD-II) trouble code directory