GM Service Manual Online
For 1990-2009 cars only

Power Sunroof System Components

The power sunroof system consists of the following components:

    • The sunroof module
    • The sunroof motor with limit switches
    • The sunroof switch
    • The sunroof glass, spoiler type with glass sliding above roof
    • The sunshade
    • The rail and track assembly upon which the sunroof glass rides
    • The power sunroof system SUNROOF 20 A fuse
    • The ground G401

Power Sunroof Operation

The power sunroof will operate with the ignition switch turned to ON. Use the 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

Express to Vent

To open the power sunroof to the vent position from the closed position turn the ignition to ON with engine OFF. Press the rear half of the sunroof switch, labeled OPEN VENT. Activating the switch applies the sunroof switch low reference to the sunroof open signal circuit 5 volt reference input, pulling the reference voltage to 0 volts. As long as the sunroof module sees a single input request from the sunroof switch open signal circuit, the sunroof module will control the sunroof motor to raise the rear of the sunroof glass to the express vent position. The sunroof glass will soft stop at the express vent position based on the inputs from the limit switches. The sunshade will have to be manually slid open. To lower the sunroof glass to a desired vent position, press the front half of the sunroof switch, labeled CLOSE and release to stop the sunroof glass. To raise the sunroof glass from the express vent position to a higher desired vent position, press the rear half of the sunroof switch, labeled OPEN VENT once. The sunroof glass will raise higher and then continue to express open. Press the sunroof switch again in either direction to stop the sunroof glass.

Express Open

The express open will work only with the glass in between the express vent and partial open positions. To express open the power sunroof, turn the ignition ON with the engine OFF. Momentarily press the rear half of the sunroof switch, labeled OPEN VENT. This will momentarily apply the sunroof switch low reference to the sunroof switch signal open signal circuit 5 volt reference input, pulling the reference voltage to 0 volts, indicating an express open request. From the express vent position the sunroof module will control the sunroof motor to raise the rear of the sunroof glass higher and then express open, sliding the sunroof glass above the roof. The sunroof glass will 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.

Close

To close the power sunroof, turn the ignition ON, engine OFF. From any sunroof glass position, press and hold the front half of the sunroof switch, labeled CLOSE. This will apply the sunroof switch low reference to the sunroof close signal circuit 5 volt reference input, pulling the reference voltage 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 motor to continue to drive the sunroof glass past the vent position until it reaches the closed position. The sunroof glass will 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 control circuit.
    • Ground is maintained to the sunroof motor close control circuit.

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

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

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

Sunroof Limit Switches

The sunroof limit switches track the position of the sunroof glass through the two limit switches:

    • The soft stop limit
    • The vent stop limit

As a limit switch closes, the 5 volt reference will be shorted to the sunroof limit switch low reference circuit, pulling the reference voltage to 0 volts. The different input combinations from the sunroof limit switch soft stop signal circuit and sunroof limit switch range signal circuit, allows the sunroof module to:

    • Understand the position the sunroof glass.
    • Soft stop the sunroof glass at the close, vent and full open positions.