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 A/Trans output speed sensor assembly has 2 internal hall-effect type sensors, and is capable of sensing both speed and direction. The A/Trans output speed sensor assembly mounts to the A/Trans case assembly and is connected to the control solenoid (w/body and TCM) valve assembly through the A/Trans wiring harness assembly and connectors. 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 front differential drive pinion (w/transfer gear) gear assembly rotates, the sensor produces a signal frequency based on the rotating speed of the machined surface of the front differential drive pinion (w/transfer gear) gear assembly.

The two sensor elements in the A/Trans 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 to the TCM. This signal is interpreted by the TCM for speed and direction and is transmitted through the GMLAN circuits to the engine control module (ECM). The electronic brake control module (EBCM) interprets and averages the 4 wheel speed inputs from the 4 wheel speed sensors and transmits this signal through the GMLAN circuits to the ECM. The ECM compares the vehicle speed signal from the TCM with the average of the 4 EBCM wheel speed sensor signals.