Module, Power Sunroof (PSM): Operation

The single pane power sunroof motor is completely controlled by the circuitry of the on-board power sunroof Electronic Control Unit (ECU). The power sunroof ECU receives battery current on a fused B(+) circuit from the Body Control Module (BCM) and has a path to ground at all times through a take out and eyelet terminal connector secured by a ground fastener to the body sheet metal. These connections allow the power sunroof ECU to function regardless of the ignition position.

However, the power sunroof ECU also monitors an input on a fused ignition output (run-accessory) circuit, and provides a source current to the sunroof switches in the Overhead Console (OHC) only when the ignition is in the ON or ACCESSORY positions, or while the accessory delay feature is active. The power sunroof ECU then monitors a separate input circuit for each switch position, which it uses to determine the proper outputs to the power sunroof motor. A positive and negative battery connection to the two power sunroof motor brushes will cause the power sunroof motor to rotate in one direction. Reversing the current through these same two brushes will cause the power sunroof motor to rotate in the opposite direction.

If the power sunroof switch and the hardwired circuitry test okay, but the power sunroof motor or the express or Excess Force Limitation (EFL) features are still ineffective following the calibration and initialization procedures, the power sunroof motor and the power sunroof ECU must be replaced as a unit.