GM Service Manual Online
For 1990-2009 cars only

The sunroof has 2 modes, or ranges, of operation. The modes permit the following functions:

    • The sunroof slides open and closed.
    • The rear of the sunroof raises and lowers from the vent position.

The sunroof module permits transition between these operating ranges. Transition does not require operator action.

The sunroof control switch controls sunroof travel. The switch is a single two-pole rocker switch. The switch is located at the overhead console. The switch provides the following grounded inputs:

    • Close and Tilt-Up
        When the forward portion of the rocker switch is depressed, the open sunroof slides toward the closed, or flush, position.
        Motion stops when the rocker switch is released or when the sunroof reaches the flush position.
        If the forward portion of the rocker switch is held down or is depressed again, the sunroof raises from the flush position to the vent position. The motion stops when the rocker switch is released or when the sunroof reaches the soft-top position in the vent direction.
    • Open and Down
        When the rearward portion of the sunroof control switch is depressed, the sunroof lowers toward the flush position.
        Motion stops when the rocker switch is released or when the sunroof reaches the flush position
        If the rearward portion of the rocker switch is held down or is depressed again, the sunroof moves in the mode to the open position. The motion stops when the sunroof reaches the soft-top position in the open direction.

The sunroof is operated by a bi-directional motor. The motor drives the sunroof to slide closed and raises the sunroof to the vent position when the following actions occur:

    • Voltage is applied to one terminal of the motor.
    • Ground is applied to the other terminal of the motor.

The sunroof lowers from the vent position slides open when voltage is applied to the other terminal. The motor is equipped with a manual drive capability. A hex head wrench inserted at the center of the motor may be used to drive the sunroof through its whole range of travel. Mechanical stops are provided in the following positions:

    • The vent direction
    • The open direction

The sunroof position is sensed by the sunroof module from a position encoding system located in the sunroof motor and drive assembly. The encoding system is represented by the following 3 limit switches:

    • LS1
    • LS2
    • LS3

The limit switches provide a grounded input to the sunroof module. You may test the input conditions by monitoring the contacts status while manually driving the sunroof through its full range of travel.

The LS1 contacts open in order to provide a 5V (ungrounded) input when the sunroof reaches or moves past the vent soft-stop position. This input initiates the soft-stop in the vent direction and prevents contact with the vent mechanical stop.

    • Initiates the soft-stop in the vent direction
    • Prevents contact with the vent mechanical stop

The contacts close in order to provide a grounded input when the lowering sunroof passes the vent soft-stop position. The input remains grounded through the flush position and into the opening range. When the opening sunroof reaches a nearly full-open position, the LS1 contacts open again in order to provide a 5V (ungrounded) input. This input initiates the soft-stop in the opening direction.

The LS2 contacts are closed in the vent position. The LS2 contacts open in order to provide an ungrounded input when the lowering sunroof reaches the flush position. The input stops travel at the flush position when the sunroof lowers. The LS2 contacts remain open while the sunroof slides open until the sunroof reaches the open soft-stop position. The contacts close again in order to provide the grounded input. This input is used in conjunction with the LS1 input. The input defines the end-of-travel soft-stop position in the open direction.

The LS3 provides an operating range input to the module. The LS3 contacts are closed (grounded input) when the sunroof operates in the slide range. The LS3 contacts open when the sunroof is in the vent range. The state of logic selects the end-of-travel input from the other switches. The LS3 contacts opening as the sunroof slides to the flush position is used in order to stop the sunroof at the flush position.

The sunroof module is equipped with a timer circuit which stops the operation of the sunroof motor after 8.4 seconds. The timer begins counting time when one of the following contacts is closed:

    • The open and down switch contact
    • The close and tilt-up switch contact

The sunroof operates until both the control switch contacts are open or until 8.4 seconds has elapsed. The timer is automatically reset when the switch is released and both control switch contacts are open.

The sunroof motor is protected by a built-in electronic circuit breaker (ECB). If the motor is overloaded or voltage is applied for an excessive amount of time, the ECB internal resistance increases. This action creates an open circuit. The resistance returns to normal only after voltage is removed from the circuit. This action restores the circuit continuity.