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Power Liftgate System: Notes

In order to obtain conclusive testing of the power liftgate system, the Controller Area Network (CAN) data bus, and all of the electronic modules that provide inputs to, or receive outputs from the power liftgate system components must be checked. Any diagnosis of the power liftgate system should begin with, the use of a scan tool and the appropriate diagnostic service information. 

Refer to  SYSTEM WIRING DIAGRAMS  article for complete circuit schematic or connector pin-out information. 

NOTE: Before any testing of the power liftgate system is attempted, the battery should be fully-charged.

Following are quick reference diagnostic tables to help when diagnosing and testing the power liftgate system.

SYMPTOM DRIVEN POWER LIFTGATE SYSTEM DIAGNOSIS TABLE

CONDITION  POSSIBLE CAUSES  CORRECTION 
LIFTGATE OPENS UNEXPECTEDLY Accidental activation or failure of open/close command switch Check for shorted or defective switch
- Failure of latch assembly Check wiring connections
- - Check for trouble codes, replace latch if necessary
- Failure of power liftgate control module Disconnect then reconnect battery to reset module. Operate power liftgate. If no function exists check for loose wire connections, repair as necessary
LIFTGATE WILL NOT OPEN/CLOSE AUTOMATICALLY Not in park/neutral or false indication Check switch status with scan tool
- Battery voltage too low Check for proper battery system voltage
- Blown fuse Check for blown fuse
- Gas prop rod failure Check condition of liftgate prop rods
- Power liftgate control module critical fault codes Check code status with scan tool
- Failure of latch assembly Check ratchet and pawl switch status with scan tool
- - Check secondary and sector switch status with scan tool
- - Check for foreign matter or damaged components preventing the operation of latch assembly. Replace latch assembly, if necessary
- - Check wire connections and for blown fuse
- Failure of power liftgate drive unit Test power liftgate drive unit
- Extreme temperatures No repair, refer to POWER LIFTGATE SYSTEM INHIBITORS 
- Vehicle speed greater than zero Test for proper operation with vehicle stopped
- Pinch sensor activated or open circuit Check pinch sensor status with scan tool
- Binding or sticking of components Establish location of binding and replace necessary components
- Check Inhibit Monitors with scan tool, refer to POWER LIFTGATE SYSTEM INHIBIT MONITORS TABLE . Repair as necessary
- Wiring problems (system or vehicle) Troubleshoot using electrical schematics. Refer to SYSTEM WIRING DIAGRAMS article
POWER LOSS DURING LIFTGATE OPERATION Wiring problems (system or vehicle) Troubleshoot using electrical schematics. Refer to SYSTEM WIRING DIAGRAMS article
- Low battery voltage Charge or replace battery
- Failure of power liftgate control module Check for diagnostic trouble codes with scan tool
- Failure of power liftgate drive unit Test power liftgate drive unit
NO AUTOMATIC LATCHING IN PRIMARY AND/OR SECONDARY POSITIONS Failure of latch assembly Check wire connections and for blown fuse
- - Check for diagnostic trouble codes and cycle with scan tool
- - Cycle latch with scan tool and check for foreign matter preventing the operation of latch assembly. Replace latch assembly, if necessary
- Binding or sticking of components Establish location of binding and replace necessary components
- Failure of power liftgate control module Check for diagnostic trouble codes with scan tool
- Door seal force too high Inspect seals for damage, mis-assembly, foreign matter or other possible obstruction
- Failure of power liftgate drive unit Check for no drive condition
- Pinch sensor activated or open/short circuit Check pinch sensor status with scan tool.
- Foreign material in latch Check and clean latch
- Check Inhibit Monitors with scan tool, refer to POWER LIFTGATE SYSTEM INHIBIT MONITORS TABLE . Repair as necessary
- Blown fuse Check fuse and replace if required
LATCH WILL NOT RELEASE FROM PRIMARY POSITION Not in park/neutral, vehicle speed greater than zero or false indication Check switch status with scan tool
- Vehicle doors locked Unlock doors
- Low battery voltage Check battery system voltage
- Blown fuse Check fuse and replace if required
- Failure of latch assembly
  1. Using the scan tool, perform the "Latch Home Position Test"
  2. If the "Latch Home Position Test" is unsuccessful, disconnect the battery for 60 seconds. Reconnect the battery and grab the outside handle switch and hold it for at least 20 seconds
  3. If the latch still will not release, use the scan tool and select "Actuates", "Latch Motor Release Direction". This will drive the motor longer than just using the outside handle switch
  4. If driving the latch by the "Latch Motor Release Direction" worked, perform the "Latch Home Position Test" before returning the vehicle back to the owner. If driving the latch by the "Latch Motor Release Direction" did not work, use the following procedure to open the liftgate and continue diagnosis as necessary. See STANDARD PROCEDURE  to open the liftgate
- Latch not "Home" Check latch sector switch circuit and attempt to "Home" latch with scan tool
- Failure of outside handle switch Check for diagnostic trouble codes and cycle with scan tool
- Failure of power liftgate control module Check for diagnostic trouble codes and cycle with scan tool
- Wiring problems (system or vehicle) Troubleshoot using electrical schematics. Refer to SYSTEM WIRING DIAGRAMS article
- Binding or sticking of components Establish location of binding and replace necessary components
- Check Inhibit Monitors with scan tool, refer to POWER LIFTGATE SYSTEM INHIBIT MONITORS TABLE . Repair as necessary
KEY FOB OR OVERHEAD CONSOLE SWITCH DOES NOT OPERATE POWER LIFTGATE Not in park/neutral, vehicle speed greater than zero or false indication Check switch status with scan tool
- Low battery voltage Check battery system voltage
- Blown fuse Check fuse and replace if required
- Failure of latch assembly Check ratchet and pawl switch status with scan tool
- - Check secondary and sector switch status with scan tool
- - Check for foreign matter or damaged components preventing the operation of latch assembly. Replace latch assembly, if necessary
- Failure of key fob Reprogram key fob
- - Replace key fob if necessary
- Failure of power liftgate control module Check for diagnostic trouble codes and cycle with scan tool
- Wiring problems (system or vehicle) Troubleshoot using electrical schematics. Refer to SYSTEM WIRING DIAGRAMS article
- Failure of Cab Compartment Node (CCN) or the Sentry Key Remote Entry Module (SKREEM) Check for diagnostic trouble codes and cycle liftgate with scan tool
- - Replace Inoperative module as necessary
- Failure of power liftgate drive unit Check for foreign matter preventing the drive unit from operating
- - Replace drive unit as necessary
- Check Inhibit Monitors with scan tool, refer to POWER LIFTGATE SYSTEM INHIBIT MONITORS TABLE . Repair as necessary
LIFTGATE DOES NOT STAY OPEN Inoperative liftgate prop rods Replace prop rods
- - Check for broken attachments
- Excessive cold or weight on liftgate Check for added weight or extreme cold climate
HIGH OPENING EFFORT Inoperative liftgate prop rods Replace prop rods
- - Check for broken attachments
- Drive unit jammed or did not disengage Troubleshoot and replace components, if necessary
- Binding or sticking of components Establish location of binding and replace necessary components
LIFTGATE CONTINUES TO CINCH CLOSED DURING POWER MODE Failure of power liftgate control module Check for diagnostic trouble codes and cycle with scan tool, refer to appropriate diagnostic information for detailed procedures
- Failure of latch assembly Check ratchet and pawl switch status with scan tool
- - Check secondary and sector switch status with scan tool
- - Check for foreign matter or damaged components preventing the operation of latch assembly. Replace latch assembly, if necessary
- Wiring problems (system or vehicle) Troubleshoot using electrical schematics. Refer to SYSTEM WIRING DIAGRAMS article
LIFTGATE CONTINUES TO OPEN DURING POWER MODE (RUNAWAY MOTOR) Failure of power liftgate module Check for diagnostic trouble codes and cycle with scan tool, refer to appropriate diagnostic information for detailed procedures
- Failure of full open switch Check switch status with scan tool
- - Replace switch, if necessary
- Failure of power liftgate drive unit Check for continuous drive condition
- Wiring problems (system or vehicle) Troubleshoot using electrical schematics. Refer to SYSTEM WIRING DIAGRAMS article
LIFTGATE OPENS VERY SLOWLY Low battery voltage Check battery electrical system voltage
- Failure of liftgate prop rods Replace prop rods, if necessary
- Binding or sticking of components Establish location of binding and replace necessary components
- Wiring problems (system or vehicle) Troubleshoot using electrical schematics. Refer to SYSTEM WIRING DIAGRAMS article
- Grade of vehicle too steep for power operation Operate liftgate manually
- Failure of power liftgate drive unit Replace power liftgate drive unit, if necessary
SQUEAKS, NOISES AND RATTLES Foreign material in door compartment Remove foreign material
- Worn/loose components Check and tighten/replace loose components
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