Circuit/System Description

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

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/Trans 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 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 OSS 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 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.