P0720 OBD-II: Output Speed Sensor Circuit
P0720 Severity
Should you fix P0720 yourself?
Identifying an OBD code is just the start of a complete diagnostic routine. Most trouble codes are caused by a sensor reporting a value that is out of range. Just replacing a sensor may not fix underlying issues. Be sure to understand the code, the part or system in your car that the code refers to, and the risks of delaying professional repair.
Proper diagnosis will save you time and money on unnecessary repairs.
Urgent codes indicate immediate action is necessary. These are urgent and significant malfunctions that can cause severe damage to the vehicle or harm the driver and passengers.
What causes OBD-II fault code P0720?
The Output Speed Sensor tells the Transmission Control Module (TCM) how fast the output shaft of the transmission is spinning so it can verify the correct gear is engaged. When the TCM receives an inaccurate or irrational signal from this sensor, it is an indication that there is an issue inside the transmission. The engine control module (PCM) or TCM will set P0720.
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What Does P0720 Code Mean?
OBD-II Code P0720 is defined as a Output Speed Sensor Circuit Malfunction
When the code P0720 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is not seeing a rational speed signal from the Output Sensor or, there is a greater than specified RPM difference between the rotational speed of the Input RPM Sensor and the Transmission Output Speed RPM Sensor. This can occur during shifting or when driving at steady speeds in the same gear. It often implies that the transmission is slipping.
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The purpose of the automatic transmission is to match the engine's optimum power and torque characteristics to the driver's desired rate of acceleration and speed by auto-selecting different gear ratios or 'speeds' to power the wheels.
P0720 Symptoms
- Check Engine Light will illuminate
- Vehicle will not shift properly
- Decrease in fuel economy
- In unusual cases, there are no adverse conditions noticed by the driver
- In some cases, there may be performance problems, such as dying when coming to a stop after driving on the freeway and/or misfire-like symptoms
Common Problems That Trigger the P0720 Code
- Defective Output Speed Sensor
- Defective Shift Solenoids
- Defective Engine Coolant Temperature Sensor
- Defective Valve Body
- Dirty transmission fluid that restricts the hydraulic passages
- Defective Output Speed Sensor wiring or connector
Common Misdiagnoses
- Engine Misfire problem
- Internal Transmission problem
- Driveline problem
Polluting Gases Expelled
- HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
- CO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas
- NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog
P0720 Diagnostic Theory for Shops and Technicians
When diagnosing a P0720 code, it is important to record the freeze frame information and then to duplicate the code setting conditions with a test drive. Pay close attention to the Output Speed Sensor vs engine load, throttle position, RPM, and road speed because a P0720 can be difficult to detect. If the signal is erratic or the values don't seem to make sense, then you may have verified the problem.
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