Diagnostic Instructions

DTC Descriptors

DTC P0721: Output Speed Sensor Performance

DTC P0722: Output Speed Sensor Circuit Low Voltage

DTC P0723: Output Speed Sensor Circuit Intermittent

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
OSS Supply Voltage	P0722, P0723	P0722, P0723	P0722, P0723	P0723
Low Reference	P0722, P0723	P0722, P0723	P0722, P0723	P0723

Typical Scan Tool Data

Output Shaft Direction

Circuit	Normal Range	Open/High Resistance	Short to Voltage	Short to Ground
Operating Conditions: Vehicle moving, normal operating temperature
OSS Signal	Forward/Reverse	Invalid/Unknown	Invalid/Unknown	Invalid/Unknown
OSS Supply Voltage	Forward/Reverse	Invalid/Unknown	Invalid/Unknown	Invalid/Unknown

Circuit/System Description

The output speed sensor (OSS) assembly has 2 internal hall-effect type sensors, and is capable of sensing both speed and direction. The OSS mounts to the A/T rear case assembly and is connected to the control solenoid (w/body and TCM) valve assembly through a wire harness and connector. The sensor faces the hybrid direct, 2-3-4 clutch housing assembly machined teeth surface. The sensor receives 8.3-9.3 volts on the OSS supply voltage circuit from the transmission control module (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 OSS assembly are spaced approximately 1/2 a tooth apart.

The electronics in the sensor combine the two signals and send a signal with a different pulse width. This signal is interpreted by the TCM for speed and direction and is transmitted through the GMLAN circuits to the engine control module (ECM) and the hybrid powertrain control module (HPCM). The ECM, HPCM, and TCM compare the OSS signal with the ABS wheel speed sensor signal.

Conditions for Running the DTC

P0721

The ignition is ON.

P0722

P0723

Conditions for Setting the DTC

P0721

The TCM detects an invalid OSS direction.

P0722

P0723

Action Taken When the DTC Sets

P0721

The TCM calculates vehicle direction.

P0722 and P0723

The TCM calculates vehicle speed based on the wheel speed sensors.

Conditions for Clearing the DTC

Diagnostic Aids

Inspect the OSS, harness, and connector pins for metallic debris and the hybrid direct, 2-3-4 clutch housing assembly machined teeth for damage or misalignment. Even one bent or misaligned tooth, and or contact with the OSS, may cause this DTC to set. Proper torque of 9-13 N·m (80-115 lb in) to the OSS mounting bolt is critical to proper OSS operation. The hybrid system is very sensitive to the OSS signal for overall operation.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information.

Special Tools

J 38522 Variable Signal Generator

Circuit/System Verification

Operate the vehicle at 16-32 km/h (10-20 mph) while observing the Transmission OSS and OSS Supply Voltage parameters on the scan tool.

Circuit/System Testing

1. Remove the OSS. Inspect the OSS, harness, and connector pins for metallic debris and the hybrid direct, 2-3-4 clutch housing assembly machined teeth for damage or misalignment. Even one bent or misaligned tooth, and or contact with the OSS, may cause this DTC to set. Proper torque of 9-13 N·m (80-115 lb in) to the OSS mounting bolt is critical to proper OSS operation. The hybrid system is very sensitive to the OSS signal for overall operation.

⇒	If damage is observed, replace the damaged component.

2. Test for 8.3-9.3 volts between the OSS supply voltage circuit and ground.

⇒	If less than 8.3 volts, test the OSS supply voltage circuit for an open/high resistance or short to ground.

⇒	If the OSS supply voltage circuit tests normal, replace the control solenoid (w/body and TCM) valve assembly.

⇒	If greater than 9.3 volts, test the OSS supply voltage circuit for a short to voltage.

3. Using a terminal test kit, connect the red lead of J 38522 to the OSS signal circuit terminal B and the black lead to the OSS supply voltage circuit terminal A.
4. Set the J 38522 Signal to 8 volts, the Frequency to 120 and the Percent Duty Cycle to 50.
5. With the ignition ON, observe the Transmission OSS parameter, The Transmission OSS parameter should display between 100-400 RPM.

⇒	If the Transmission OSS is not within the specified range, test the Transmission OSS signal circuit for an open/high resistance, short to ground, or a short to voltage.

⇒	If the circuit tests normal, replace the control solenoid (w/body and TCM) valve assembly.

⇒	If the Transmission OSS is within the specified range, replace the OSS.

Component Testing

Perform the Control Solenoid Valve and Transmission Control Module Assembly Output Shaft Speed Input Test.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. Perform the Output Speed Sensor Replacement.
2. Control Module References for control solenoid (w/body and TCM) valve assembly replacement, setup, and programming.
3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection.
4. Perform the Control Solenoid Valve and Transmission Control Module Assembly Output Shaft Speed Input Test.