Power Liftgate - Operation

OPERATION

The components and features of the power liftgate system are designed to provide the vehicle operator with convenient and safe access to the cargo area of the vehicle. The power liftgate components convert electrical energy produced by the electrical system of the vehicle into the mechanical action necessary to latch, unlatch, raise and lower the liftgate with the simple touch of a button or the slight pull of the exterior liftgate latch handle.

Battery voltage is supplied to the Power Liftgate Module (PLGM) through a fused B(+) fuse in the Totally Integrated Power Module (TIPM) so the PLGM can operate regardless of the ignition switch status. The PLGM monitors many hard wired switch and sensor inputs from the liftgate latch and cinch mechanisms, the Power Drive Unit (PDU), the D-pillar power liftgate switch, the exterior latch handle power liftgate switch, the overhead console power liftgate switch, both pinch sensors and the thermistor in the right pinch sensor.

The PLGM also monitors many electronic message inputs received over the Controller Area Network (CAN) data bus network. Electronic message inputs include: ignition switch status, Transmission Range Sensor (TRS) status, vehicle speed, Remote Keyless Entry (RKE) commands, vehicle theft alarm status, power lock system status and (if equipped) liftgate flip-up glass ajar switch status. In response to those many inputs, the PLGM logic allows it to properly control numerous hard wired outputs that operate the power liftgate latch and cinch mechanisms and the PDU that opens and closes the liftgate as well as the chime tone generator that provides audible indications of the power liftgate status. The PLGM will also place electronic messages on the CAN data bus indicating the liftgate status and many of the hard wired sensor inputs it receives for use by other electronic modules in the vehicle.

Operation of the power liftgate requires the transmission be in the Park or Neutral positions, the vehicle speed not be greater than zero and that the liftgate flip-up glass is closed. When the vehicle is also unlocked, the power liftgate can be opened by lifting the exterior liftgate latch handle. If the vehicle is locked, a single press of the overhead console power liftgate button or two presses within five seconds of the RKE Liftgate button on the FOB with Integrated Key (FOBIK) will unlock and open the liftgate. The fully open liftgate can be closed automatically by depressing the D-Pillar switch or the overhead console switch one time or by depressing the RKE Liftgate button on the FOBIK twice within five seconds. The fully open liftgate can also be closed manually by pulling it down in the same manner as a non-power liftgate.

The PLGM also confirms safety requirements are met before supplying power to the PDU to begin any power cycle. The PLGM software detects obstructions through inputs from the two pinch sensors as well as by monitoring the resistance to travel of the PDU. When a sufficient obstruction is detected, the PLGM will reverse the direction of the liftgate. Also, an exterior liftgate handle pull during an automatic Close cycle will reverse the power liftgate operation to Open, while an exterior liftgate handle pull during an automatic Open cycle will cancel the cycle and put the power liftgate into full manual operation. In addition to the Electronic Vehicle Information Center (EVIC) customer programmable audible power liftgate chime alerts, when a customer programmable feature is set to Flash Lamps With Lock, two flashes of the exterior signal lamps will occur at the beginning of each power liftgate Open or Close cycle.

The PLGM continually monitors all of the power liftgate system circuits and components, and will store a Diagnostic Trouble Code (DTC) for any problem it detects. The PLGM uses an adaptive memory which allows it to relearn and adapt to changes in the system that might occur due to component wear or ambient conditions. If a power liftgate system component is replaced or a liftgate adjustment is made, the PLGM is required to relearn the effort and time required to open or close the liftgate. This learn cycle can be initiated with a diagnostic scan tool. .

The hard wired circuits and components of the power liftgate system may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the power liftgate system or the electronic controls or communication between other modules and devices that provide some features of the system. The most reliable, efficient, and accurate means to diagnose the power liftgate system or the electronic controls and communication related to system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.