P0721
DTC P0721
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0721
- Output Speed Sensor Performance
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The A/Trans Output Speed Sensor Assembly has 2 internal hall-effect type sensors, and is capable of sensing both speed and direction. The output speed sensor is internal to the transmission and mounts to the A/Trans case assembly and is connected to the transmission control module (TCM) through the control solenoid valve assembly and transmission internal harness. The A/Trans Output Speed Sensor Assembly faces the park gear machined teeth surface. The sensor receives 8.3-9.3 volts on the OSS supply voltage circuit from the TCM. As the output shaft rotates, the sensor produces a signal frequency based on the machined surface of the output shaft.
The two sensor elements in the output speed sensor assembly are spaced approximately 1/2 a tooth apart.
* When the vehicle is moving in a forward direction, sensor A detects a particular tooth before sensor B.
* When the vehicle is moving in a reverse direction, sensor B detects a particular tooth before sensor A.
The electronics in the sensor combine the two signals and send a signal with a different pulse width. This signal is interpreted by the transmission control module for speed and direction and is transmitted through the serial data circuits to the engine control module (ECM) and the hybrid powertrain control module. The ECM, hybrid powertrain control module, and transmission control module compare the output speed sensor signal with the antilock brake system (ABS) wheel speed sensor signal. The TCM is part of the control solenoid valve assembly and is not serviced separately. The hybrid powertrain control module is part of the drive motor generator power inverter module and is not serviced separately.
Conditions for Running the DTC
The vehicle is ON.
Conditions for Setting the DTC
The transmission control module detects an invalid Automatic Transmission Output Shaft Speed Sensor direction.
Action Taken When the DTC Sets
The hybrid powertrain control module 1 calculates vehicle direction based on the drive motor direction. The vehicle speed is calculated by the antilock brake system (ABS) wheel speed sensors.
Conditions for Clearing the DTC
DTC P0721 is a Type A DTC.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics Electrical Diagrams
Connector End View Reference
Component Connector End Views Hybrid/EV Battery Pack X1
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Programming and Relearning for scan tool information.
Special Tools
EL 38522 - Variable Signal Generator
Circuit/System Verification
1. Operate the vehicle at 16-32 km/h (10-20 mph), observe the scan tool Transmission OSS parameter. The reading should be greater than 150 RPM and not drop out.
2. Observe the scan tool OSS Supply Voltage parameter. The reading should display OK.
Circuit/System Testing
Perform the Control Solenoid Valve and Transmission Control Module Assembly Output Shaft Speed Input Test Control Solenoid Valve and Transmission Control Module Assembly Output Shaft Speed Input Test.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Transmission Replacement Transmission Replacement for transmission removal.
* Automatic Transmission Wiring Harness and Output Speed Sensor Removal Automatic Transmission Wiring Harness and Output Speed Sensor Removal and Automatic Transmission Wiring Harness and Output Speed Sensor Installation Automatic Transmission Wiring Harness and Output Speed Sensor Installation for Automatic Transmission Output Shaft Speed Sensor replacement.
* Control Module References Programming and Relearning for Control Solenoid Valve Assembly and Transmission Control Module Assembly replacement, programming, and setup.
* Perform the Reset Transmission Adapts Programming and Relearning following all transmission related repairs.