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P0720 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

Output Speed Sensor Circuit Malfunction

Meaning

Motor vehicles use the power transmission system to transport the energy produced by the engine to the vehicle's wheels. The transmission system uses two sensors, the input and the output speed sensor, to regulate the vehicle's movement by transmitting information to the vehicle's power control module. The output speed sensor, in specific, measures the speed at which the car is moving. It then transmits this information to the vehicle's Power Control Module (PCM). This information is essential as it helps the PCM to determine when the gear needs to be changed. This information also comes in handy for the PCM when adjusting the torque converter and displaying the vehicle's speed on the speedometer. P0720 occurs when the output speed sensor stops sending signals to the PCM or the signals being issued by the output sensor are too erratic.

Causes

There can be more than one reason for the DTC P0720 to occur. Some of the most common causes are listed below:

  • There can be a malfunction in the output speed sensor located on the long side of the output shaft.
  • It is also a possibility that the input shaft speed sensor has malfunctioned, resulting in a P0720. The input shaft speed sensor is responsible for measuring the speed of the torque converter’s rotations, also referred to as internal revolutions. 
  • The DTC P0720 may also result from faulty or frayed wiring in the connectors linked to the output speed sensor. 
  • It may also be the case that the connectors linked to the output speed sensor are loose. P0720 can result in such a situation. 
  • The transmission system uses a liquid for lubrication and cooling purposes. This liquid is referred to as a transmission fluid. The transmission fluid performs tasks such as lubricating the moving parts in the transmission system and cooling down the transmission energy. P0720 may also occur in case of a scarcity of the transmission fluid in the output speed sensor. 
  • Transmission solenoids operate the transmission fluid in the transmission system. These solenoids are regulated by the PCM, using electric signals. A malfunction in the transmission solenoids can also result in the emergence of P0720.
  •  A fault in the Power Control Module (PCM) may also be the reason for the false detection of DTC P0720.

Symptoms

In addition to the malfunction lamp being illuminated on your dashboard, the following symptoms may surface in the presence of DTC P0720: 

  • You may face difficulty while shifting gears in the case of DTC P0720.
  • An impairment between the speedometer and the actual car speed may also signify DTC P0720.
  • Decreased speed efficiency is another one of the symptoms of fault code P0720.
  • If fault code P0720 occurs, your engine may stall and occasionally misfire.

Diagnosis

Self Diagnosis:

In the case of DTC P0720, self-diagnosis may not always be a feasible option, primarily due to the location of the output speed sensor and the reason that the fault code can be caused due to multiple factors. However, a visual examination of the output speed scanner can track down any frayed or damaged wiring around the connectors and the sensor itself. If you cannot spot any visible anomalies, it is always recommended that you have your vehicle examined by a professional technician.

Professional Diagnosis:

The technician will start with an initial check that involves scanning the PCM with an OBD scanner. This would allow the technician to freeze-frame fault code data and detect the presence of P0720. The OBD scanner will help the technician to see if any other underlying fault codes are linked to the DTC P0720. 

Once the technician has identified the problem, they would reset and clear the default code data before restarting the vehicle’s engine to check if the fault code resurfaces or not. If the problem persists, the technician will start off by checking the connector and linked wires for any corrosion or damage. Damaged cables or connectors, if detected, would then have to be replaced. After replacing the damaged components, the technician should reset your vehicle’s PCM and check if the fault code disappears or not. 

If corroded wires and connectors are not the cause, then it is likely that the output speed sensor needs to be checked for damage or scarcity of transmission fluid. If there is a shortage of transmission fluid in the output speed sensor, then the technician will restore the amount of the transmission fluid to the manufacturer's specified level. If doing so does not help eliminate P0720, the technician will check the output speed sensor's circuit for any leakages or breaks. If the circuit is open, the technician will make the necessary replacements to have the circuit back up and running. 

If the fault code P0720 persists despite taking all of the steps mentioned above, the technician may suggest replacing the PCM itself. 

Common mistakes

It is often the case that technicians may resort to replacing the output speed sensor without checking the amount of transmission fluid in the system. Ensuring that the technician checks for transmission fluid levels may help save you some bucks, as this would prevent unnecessary replacement of the output speed sensor.  

How Serious Is This Code?

DTC P0720 may be negligible, but not having the trouble code fixed may result in your vehicle's transmission being disrupted in the long run. Running your vehicle for prolonged periods in the presence of fault code P0720 may eventually damage your vehicle's engine performance.  

What repairs can fix the code?

Following steps can be taken to eliminate P0720:

  • Replace the output speed sensor
  • Replace the PCM
  • Replace any damaged wiring or connectors
  • Maintain transmission fluid at the optimum level

Related codes

  • P0715
  • P0721
  • P0722
  • P0723

Conclusion

Regular visits to the technician and keeping up with the manufacturer’s recommended maintenance checks can help prevent OBD P0720.

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