What is the P0721 fault number? What is the Output Shaft speed (OSS) sensor range/performance failure description? How do I fix the P0721 fault code What are the symptoms and causes for the P0721 fault code
What is the P0721 Fault code? What does it signify?
Fault code 00721 is related to the transmission output speed (OSS) sensor. Triggered when the OSS sensor sends an abnormal or unanticipated voltage signal to the powertrain controller module (PCM), or the transmission control manager (TCM). This code is only applicable to vehicles equipped with automatic transmission.
The transmission output shaft speed sensor’s primary function is to provide data to the PCM/TCM on the shaft rotation speed. This data, along with other transmission speed sensor input data, is used by PCM/TCM for shifting strategies and hydraulic pressure calculations for each gear. It manages the shift solenoids, allowing the transmission to be shifted into the correct gear at the right time. In certain applications, the OSS sensor also determines vehicle speed.
Code P0721 will be set if the PCM/TCM detects that the voltage signal coming from the output shaft speed sensor exceeds the manufacturer’s specifications or is not working properly.
P0721 fault codes can be found on vehicles made by: Hyundai, Dodge and Lincoln, Mercedes-Benz. Chevrolet. Duramax. Honda. Saturn. Acura. Ford. Volvo. Volkswagen. Jeep. Allison. BMW.
What is the P0721 Fault Code?
Below are some reasons to set fault code P0721:
- – Corroded, damaged, burned, shorted or disconnected wiring and/or connectors to OSS sensor
- – Defective gearbox output shaft speed sensor
- – Defective transmission input shaft speed sensor
- Low levels of transmission fluid
- – Transmission oil that is dirty or has gone bad
- Fluid passage lines and transmission filters clogged
- – Defective shift solenoid(s)
- Faulty engine-drivability sensors (in certain cases other faulty sensors may cause this code be set).
- – Defective transmission fluid temperature (TFT) sensor
- – Defective PCM/TCM (rarely)
Note: Some vehicles have the OSS sensor aligned with TFT sensor. If there is a fault within the TFT sensor, or the associated wiring, the OSS sensors may also fail.
What are the symptoms for P0721 Trouble Code?
You may experience the following symptoms if your vehicle has the code P0721:
- – Illumination for the check engine light
- – Incorrect or delayed shifting
- – Transmission stuck at any gear
- Speed (km) indicator not working or reading incorrectly
- – May exhibit motor misfire-like symptoms
- PCM can limit vehicle speed through failsafe mode
- – Significant rise in fuel consumption
- – Other fault codes can be set
How to Fix the P0721 Fault Code
The following repairs may be able to resolve the P0721 fault code:
- – Replacing damaged wires or connectors with the OSS sensor
- – Replacing the faulty OSS Sensor
- – Replacing the defective speed sensor for the input shaft
- – Draining the transmission fluid and refilling it
- – Replacing transmission filter
- – Cleaning clogged transmission line
- Repairing transmission fluid leaks
- – Replacing a defective shift solenoid (s)
- – Replace the TFT sensor (Transmission Fluid Temperature)
- – Replacement PCM/TCM
Technicians should examine the damage to the output velocity sensor, or any other components, after replacing the defective parts. If the sensor fails because of an engine leak, it is necessary to fix the leak and not just the sensor.
How serious is the P0721 Fault code?
You should immediately address code P0721 if your speedometer doesn’t read correctly. An accident or traffic ticket can be issued if you don’t know how fast your vehicle is moving. Fault code P0721 is annoying. Transmissions can become stuck in any gear, or may cause delayed, erroneous shifts. This could indicate a serious problem which needs to be addressed immediately.
