DTC P1627 Buick

Description

The HVAC mode and temperature doors are operated with 5-wire actuators. Each actuator has two control circuits that carry a 12 volt Pulse Width Modulated (PWM) signal from the HVAC module when the doors are commanded to move in either direction. Each actuator also contains a position sensor. The position sensors contain three circuits; a 5 volt supply, a sensor ground, and a position signal circuit. The position signal is used by the HVAC module to monitor the door position. Upon each ignition cycle, the HVAC module relearns the full open and full closed positions of each door. If the desired positions cannot be reached during normal operation or, if a learned position is out of range, a failure is detected. All of the circuits are also monitored, either directly or indirectly, for open short circuit faults.