Circuit Description

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The steering wheel position sensor inputs to the rear wheel steering control module consists of 3 digital input circuits, phase A, phase B, and index marker pulse and 1 analog signal circuit. The analog signal is a class 2 message from the TBC. The steering wheel position sensor supply voltage is between 4.9--5.1 volts.

Phase A and phase B circuits are digital pulse signals whose output represents one degree of steering wheel rotation. When observing the phase A data and the phase B data parameters on the scan tool, the parameters will not have the same value at the same time. When the steering wheel is rotated, the phase A data and the phase B data parameters will be shown as high or low on the scan tool.

The marker pulse is a digital pulse that is displayed as high on the scan tool for 20° only when the steering wheel angle is between -10 and +10°.

Steering wheel position sensor, analog signal, voltage is at or near 2.5 volts with the wheels at center voltage increases/decreases for less than 1 full turn (+/- 225°) then plateaus for remainder of wheel travel. The body control module (BCM), which receives an analog steering position sensor input, transmits steering position data on the serial data line. The rear wheel steering control module monitors the serial data information as an added fail-safe for the steering position sensor circuitry. Battery voltage is supplied to the digital portion of the steering wheel position sensor from the cruise control fuse. The analog portion of the steering wheel position sensor is supplied a 5-volt reference from the BCM. This circuit is also used for a lamp dimming function.