Power Lock System

The power lock system uses non-switched battery current received through a fused B(+) to the Body Control Module (BCM) so that the system remains operational regardless of the status of the ignition system. The BCM is the primary power lock system controller. On vehicles equipped with a Drivers Door Module (DDM), the power lock switches are hardwired direct to the DDM. The DDM then sends the switch status via Controller Area Network (CAN) to the BCM. For those vehicles equipped with a Smart Motor instead of the DDM, the power door lock switches are hardwired directly to the BCM. The BCM, DDM and Passenger Door Module (PDM) all communicate with each other and with other electronic modules in the vehicle over the CAN bus.

When the BCM receives an input from a door module or from a switch on a Smart motor system, it responds to these request messages by providing the appropriate outputs to each of the power lock motors to lock or unlock each of the door latches. The BCM also monitors a hardwired input from the power liftgate module and electronic message inputs indicating automatic transmission gear selector position and vehicle speed. The BCM uses all of these inputs and internal programming to determine whether or not to provide the output necessary to operate the liftgate latch release motor.

The BCM also stores the power lock system Customer Programmable feature settings received over the CAN data bus from the Electronic Vehicle Information Center (EVIC). The BCM uses these settings and internal programming along with hardwired and electronic message inputs to determine the proper outputs needed to produce each of the appropriate power lock system features.

The power lock system circuits are continually monitored and controlled by the microprocessor and software contained within the BCM. When the BCM monitors a problem in any of the power lock system circuits or components, it stores a fault code or Diagnostic Trouble Code (DTC) in its memory circuit. The hardwired circuits between components related to the power lock system may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes appropriate SYSTEM WIRING DIAGRAMS and details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.

However, conventional diagnostic methods will not prove conclusive in the diagnosis of the power lock system or the electronic controls or communication between other modules and devices that provide features of the power lock system. The most reliable, efficient, and accurate means to diagnose the power lock system or the electronic controls and communication related to power lock system operation, as well as the retrieval or erasure of a DTC requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.