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P0720 OBD-II Trouble Code: Output Speed Sensor Circuit Malfunction

check engine light

P0720 code definition

The P0720 trouble code notes an error with the output speed sensor circuit.

What the P0720 code means

The P0720 code is a standard OBD-II trouble code that detects an issue with the output speed sensor circuit. The powertrain control module (PCM) relies on a signal from the output speed sensor, so that it can determine the correct shift strategy and send that information to the transmission. If the PCM fails to receive information from the output speed sensor, or the information is sporadic, erratic, or simply not a slow and steady increase, the P0720 trouble code will be triggered.

What causes the P0720 code?

There are a handful of different issues that can result in the P0720 code, including:

  • Malfunctioning output speed sensor
  • Malfunctioning input speed sensor
  • Damaged or corroded wires, or loose connectors
  • Contaminated or low transmission fluid
  • Faulty engine drivability sensors
  • Malfunctioning shift solenoids
  • In very rare cases, a defective PCM

What are the symptoms of the P0720 code?

When the P0720 code is detected, the check engine soon warning light will likely illuminate. The vehicle will also may have engine and transmission issues, including an inability to shift, a harsh shift feel, an erratic or malfunctioning speedometer, hesitation and misfiring from the engine, and potentially stalling. The vehicle may also experience a decrease in fuel efficiency.

How does a mechanic diagnose the P0720 code?

The P0720 code will be diagnosed using a generic OBD-II trouble code scanner. A reputable technician will start by examining the freeze frame data from the trouble code scanner, which will give them information about the code, and will allow them to search for additional trouble codes that have been detected. The trouble codes will then be reset, and the vehicle restarted and briefly driven. If the P0720 code does not return, it likely is an intermittent issue, rather than a problem with the output speed sensor.

If the P0720 trouble code is still detected, then the technician should begin by examining any basic issues that may be triggering the code, such as the wires, connectors, and transmission fluid. When any issue is found, it should be resolved, and the codes should be reset.

If the code persists, the mechanic will test the output speed sensor’s ground signals and reference voltage. If either circuit is open, it will need to be replaced.

Common mistakes when diagnosing the P0720 code

The most frequent mistake made when diagnosing the P0720 trouble code comes from failing to follow the OBD-II trouble code diagnosis protocol. All steps should be followed in order to make sure that the inspection and repair is both thorough and efficient.

Failure to follow the trouble code diagnosis protocol can result in the output speed sensor being erroneously replaced when a much simpler issue was the problem.

How serious is the P0720 code?

In most cases the P0720 code does not keep a car from being drivable. However, the effects of the code can get worse if it is not repaired, and further damage can be caused to the transmission.

What repairs can fix the P0720 code?

Repairs for the P0720 trouble code include:

  • Replacement of the output speed sensor
  • Replacement of the input speed sensor
  • Replacement of the wires or connectors
  • Drain and refill of the transmission fluid
  • Replacement of the PCM

Additional comments for consideration regarding the P0720 code

The P0720 code is often joined by an input speed sensor code.

After the faulty components have been replaced, a technician should check to see if other engine issues caused damage to the output speed sensor or other components. For example, if the sensor failed due to an engine leak, then the leak needs to be fixed, not just the sensor.

Need help with a P0720 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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