GM Service Manual Online
For 1990-2009 cars only

Power Sunroof System Components

The power sunroof system consists of the following components:

    • Sunroof module
    • Position Encoding System (PES) (limit switches)
    • Sunroof switch.
    • Sunroof motor
    • Sunroof glass (spoiler type, with glass sliding above roof)
    • Sunshade
    • Rail and track assembly upon which the sunroof glass rides
    • Power supply for the sunroof module: SUNROOF 20 A fuse
    • Ground from G302

Power Sunroof Operation

The power sunroof will operate with the ignition switch turned to Accessory or RUN. Once the ignition switch is turned to OFF the sunroof will continue to operate until any door is open or when the Retained Accessory Power (RAP) has timed out. For a description and operation of the RAP operation, refer to Retained Accessory Power (RAP) Description and Operation in Retained Accessory Power.

Use the rocker type sunroof switch, located in the front center of the headliner, to command the sunroof to :

    • Vent
    • Express Open
    • Close

Pressing the sunroof switch rearward, the sunroof glass will slide from:

    • Closed position to the vent position.
    • Vent position to the open position.

Pressing the sunroof switch forward, the sunroof glass will slide from:

    • Open position to the vent position.
    • Vent position to the closed position.

To Express Open to Vent

To open the power sunroof to the vent position from the closed position, momentarily press the sunroof switch rearward. This will apply the sunroof switch low reference to the sunroof open signal circuit (5 volt reference) input, pulling the reference voltage down to 0 volts. As long as the sunroof module only see a single input request from the sunroof switch (open signal circuit), the sunroof module will automatically (express open) open the sunroof glass to the full vent position, raising the rear of the glass upward. The sunroof glass will stop (soft stop) at the full vent position based on the inputs from the limit switches. The sunshade will have to be manually slid open. To stop the sunroof glass in a desired vent position other than full vent, toggle the sunroof switch to either direction as the sunroof glass is raising upward.

Express Open

The express open will work only with the glass in between the full vent and partial open positions. To express open the power sunroof, momentarily press (less than 1.5 seconds) the sunroof switch rearward once. This will apply the sunroof switch low reference to the sunroof switch signal open signal circuit (5 volt reference) input, pulling the reference voltage down to 0 volts momentarily. The momentary 0 volts input to the sunroof module indicates an express open request. The sunroof module will control the sunroof motor circuits to automatically slide (express open) the sunroof glass above the roof. The sunroof glass will stop (soft stop) at the full open position based on the inputs from the limit switches. As the sunroof glass expresses open so will the sunshade. To stop the sunroof glass in a desired position other than to the express open position:

    • As the sunroof is expressing open, press the sunroof switch again (in either direction) to stop the movement.
    • Instead of momentarily pressing the sunroof, maintain pressing (more than 1.5 seconds) the sunroof switch rearward and when the sunroof glass reaches the desired position, then release the switch.

Close

To close the power sunroof press and hold the sunroof switch forward, this will apply the sunroof switch low reference to the sunroof close signal circuit (5 volt reference) input, pulling the reference voltage down to 0 volts. The sunroof switch close signal input to the sunroof module needs to have constant 0  volts applied (switch pressed) to allow the sunroof module to continue to control the sunroof motor circuits to drive the sunroof glass past the vent position until it reaches the closed position. The sunroof glass will stop (soft stop) at the closed position based on the inputs from the limit switches. To close the sunshade, this will have to be manually slid closed.

Sunroof Motor

The sunroof has a bi-directional motor. When the sunroof motor is not operating both circuits are grounded. When the sunroof motor drives the sunroof glass in the direction from the closed to vent or vent to open position, the following occurs:

    • Voltage is supplied to the sunroof motor open circuit.
    • Ground is maintained to the sunroof motor close circuit.

When the sunroof motor drives the sunroof glass in the direction from the open to vent or vent to closed position, the following occurs:

    • Voltage is supplied to the sunroof motor close circuit.
    • Ground is maintained to the sunroof motor open circuit.

The sunroof module is equipped with a timer circuit which stops the operation of the sunroof motor after 8 seconds.

Position Encoding System (PES)

The Position Encoding System (PES) tracks the position of the glass through two limit switches:

    • Soft Stop limit
    • Vent limit

The sunroof module monitors the limit switches and based on the inputs determines the position of the sunroof glass. As a limit switch closes, the 5 volt reference will be shorted to the sunroof limit switch low reference circuit, pulling down the 5 volt reference to 0 volts.

The sunroof module understands the position of the sunroof glass based on the different input combinations through the sunroof limit switch soft stop signal and sunroof limit switch open vent signal circuits.