Speed sensor failures and solutions to code P0720

The P0720 code means that the sensor that measures the speed at which the output shaft of the transmission rotates is failing or has a faulty connection. This information is necessary so that the engine computer can calculate the correct rpm and make gear changes smoothly.

This signal appears when the car's computer does not receive the signal from the speed sensor, or when it is erroneous or intermittent.

What does the P0720 code mean?

The DTC P0720 indicates a problem in the communication between the PCM and the OSS sensor. This sensor provides key information for transmission control. The absence or intermittency of this signal triggers the fault code.

Symptoms of Fault Code P0720

• The engine fault indicator has been activated.
• The speedometer is not showing the actual speed of the vehicle. 
• Speed changes occur with delay or difficulty

Causes of P0720 code activation

1. Sensor system problems: OSS and ISS sensor cables may be damaged and sensors may be defective. 
2. Improper transmission fluid level or quality: A low level or the presence of contaminants in the fluid could affect the operation of the transmission. 
3. Failure of control components: The shift solenoids, which control gear changes, could be faulty.

Solutions for the P0720 fault code

To remove the P0720 code and repair the associated fault, it is recommended to follow these procedures:

1. Access the OSS sensor and remove the gear: Carefully examine the gear teeth for wear, breakage, or missing. If there is any damage, proceed to replace it with a new one.
2. Inspect OSS sensor wiring: Identify frayed wires, cuts, loose connections, or corroded terminals, then clean or replace any deteriorating components. Also, check that there is no excessive resistance in the cables, which could indicate a problem with the wiring. If you encounter any abnormal resistance, trace the route of the wires through the circuit. This will help you find the cause of the problem.
3. Check the integrity of the circuit: Disconnect the wires from the OSS sensor to isolate the circuit and check for any ground cuts. If disconnecting the cables causes any change in the operation of the vehicle, it is likely that there is a short circuit.

1. Measure the resistance of the OSS sensor: Using a multimeter, measure the electrical resistance of the sensor and disconnect it from the wiring, then compare the value obtained with the data specified by the manufacturer. If you notice that the resistor is not within range, the sensor will need to be replaced.
2. Verify electrical circuit continuity: With an electrical diagram, follow the route of the wires from the OSS sensor to the PCM and make sure the electrical signal reaches the PCM without interruption.

Finally, make sure that you meet the manufacturer's specifications and that you are using the appropriate tools to achieve a flawless result.

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