Volt

DTC P077B

The transmission output shaft speed sensor has 2 internal hall-effect type sensors, and is capable of sensing both speed and direction. The transmission output shaft speed sensor mounts to the A/Trans case assembly and is connected to the control solenoid valve assembly through a wire harness and connector. The sensor faces the front differential drive pinion, w/transfer gear, gear 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 transmission output shaft speed sensor 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. The ECM, hybrid powertrain control module, and TCM compare the OSS signal with hybrid motor speed/direction and the ABS wheel speed sensor signal.

The hybrid powertrain control module or the transmission control module detects an incorrect OSS direction.

Hybrid Powertrain Control Module

The hybrid powertrain control module calculates OSS direction based on drive motor 1 and drive motor 2 direction.

Transmission Control Module

The hybrid powertrain control module 1 and ECM use the ABS wheel speed to calculate vehicle speed.

Hybrid Powertrain Control Module

P077B is a Type A DTC.

Transmission Control Module

P077B is a Type A DTC.

Inspect the output speed sensor, harness, connector and control solenoid valve assembly pins for metallic debris and output shaft machined face for damage or misalignment. Proper torque of the output speed sensor mounting bolt is critical to proper output speed sensor operation. Use a terminal test kit for any test that requires probing the control solenoid valve assembly harness connector or a component harness connector.

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electronic Component Description

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

EL 38522 Variable Signal Generator

1. Verify that DTCs P0721, P0966, P0967, P0969, P0970, P0971, P0973, P0974, P0976, P0977, P2720, P2721, P2728, P2729, or P2730 are not set.

⇒	If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Operate the vehicle at 16-32 km/h (10-20 mph) while observing the Transmission Data OSS Direction parameter on the scan tool. The OSS Direction parameter should match vehicle direction.

⇒	If the OSS parameter corresponds with the vehicle direction and the DTC is set in the hybrid powertrain control module and not the transmission control module, replace the T6 power inverter module.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for Drive Motor Generator Power Inverter Module, also called the power inverter module, and Control Solenoid Valve Assembly and Transmission Control Module Assembly replacement, programming, and setup.