Liftgate System Diagnosis
Liftgate System Diagnosis
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
The power liftgate system is a standard liftgate that has an added electric motor, hydraulic pump, a hydraulic arm, and an electric latch/cinch that can open and close the liftgate with no customer input. The liftgate can be both manually or automatically open and closed. Automatic opening or closing of the liftgate can be done through the interior liftgate switch, pushing either the open or close switch at the liftgate, or selecting open or close on the remote keyless transmitter. The automatic liftgate function can be disabled using the interior liftgate on/off control switch.
Diagnostic Aids
Power liftgate function will only be allowed if certain operating criteria are met. Any of the following may cause the power liftgate not to function:
* Vehicle is not in park
* System voltage is below 10.5 V
* Engine is cranking
* The vehicle doors are locked
* A liftgate control module DTC is set
* Liftgate motor excess current is detected which may be caused by a misaligned liftgate striker
* Interior trim and/or liftgate wedge/bumper misalignment
A power liftgate that will not fully open may be caused by kinked or twisted hydraulic lines.
Whenever the liftgate control module loses power or is disconnected, the ignition must be cycled OFF then ON in order to reactivate the liftgate control module.
An open or shorted accessory wake up ignition circuit between the engine control module and transmission control module will cause the power liftgate to work when the ignition is ON but not work when the ignition is OFF.
Reference Information
Schematic Reference
Liftgate Schematics Liftgate Schematics
Connector End View Reference
Component Connector End Views Sunshade - Left Front
Description and Operation
Liftgate Description and Operation Liftgate
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON.
2. Verify the K39 liftgate control module is programmed with the latest software.
• If the software is not the latest
Refer to Control Module References Control Module References for liftgate control module replacement, programming and setup.
• If the software is the latest
3. Verify the K39 liftgate control module does not have any current DTCs set.
• If the K39 liftgate control module has current DTCs set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle
• If the K39 liftgate control module does not have any current DTCs set
4. Verify DTC B2494 or B153F is not set as a history DTC.
• DTC B2494 is set only as history
Refer to Liftgate Release Switch Replacement Liftgate Release Switch Replacement
• DTC B153F is set only as history
Refer to Liftgate Side Upper Sensor Replacement (Equinox) Liftgate Side Upper Sensor Replacement (Equinox)Liftgate Side Upper Sensor Replacement (Terrain) Liftgate Side Upper Sensor Replacement (Terrain)
• If the K39 liftgate control module does not have any history DTCs set
5. Verify the scan tool Liftgate Mode Switch is between 125 counts and 350 counts and changes to 245 counts while rotating the liftgate control switch-interior.
• If not between 125 counts and 350 counts or does not change
Refer to Liftgate Interior Release Open/Close Switch Malfunction - DTC B396C or B396D B396C.
• If between 125 counts and 350 counts and changes
6. Verify the scan tool Liftgate Front Control Switch parameter changes between Inactive and Active when pressing the liftgate control switch-interior.
• If the parameter does not change
Refer to Liftgate Interior Release Open/Close Switch Malfunction - DTC B396C or B396D B396C.
• If the parameter changes
7. Liftgate Closed, verify the scan tool Liftgate Latch Pawl Switch, Liftgate Latch Ratchet Switch, and Liftgate Latch Sector Switch parameters are as listed below
* Liftgate Latch Pawl Switch parameter Close
* Liftgate Latch Ratchet Switch parameter Close
* Liftgate Latch Sector Switch parameter Inactive
• If any of the parameter are not as listed
Refer to Liftgate Latch Switches Malfunction - DTC B153A B153A.
• If the parameters are as listed
8. Verify the scan tool Liftgate Handle Switch parameter changes between Active and Inactive when pressing the liftgate handle switch.
• If the parameter does not change
Refer to Liftgate Handle Switch Malfunction - DTC B2494 Liftgate Handle Switch Malfunction.
• If the parameter changes
9. Using either the power door lock switches or the keyless entry transmitter, LOCK all doors then UNLOCK all doors. This will set the liftgate module door lock status to unlock.
10. Verify the liftgate will manually open by pressing the pressing the liftgate handle switch.
• If the liftgate does not open
Refer to Liftgate Latch Release/Cinch Malfunction - DTC B2495 B2495
• If the liftgate opens
11. Liftgate Open, verify the scan tool Liftgate Secondary Obstacle Detection parameter is between 3V-3.5V.
• If not between 3V-3.5V
Refer to Liftgate Object Sensor Malfunction - DTC B153F B153F.
• If between 3V-3.5V
12. Liftgate Open, verify the scan tool Liftgate Latch Pawl Switch, Liftgate Latch Ratchet Switch, and Liftgate Latch Sector Switch parameters are as listed below
* Liftgate Latch Pawl Switch parameter Open
* Liftgate Latch Ratchet Switch parameter Open
* Liftgate Latch Sector Switch parameter Inactive
• If any of the parameter are not as listed
Refer to Liftgate Latch Switches Malfunction - DTC B153A B153A.
• If the parameters are as listed
13. Verify the scan tool Liftgate Angle is between 0° and approximately 70° and changes as the liftgate opens and closes.
• If not between 0° and approximately 70° or does not change
Refer to Liftgate Angle Sensor Malfunction - DTC B153E B153E.
• If between 0° and approximately 70° and changes
14. Verify the scan tool Liftgate Rear Close Switch parameter changes between Active and Inactive when pressing the liftgate close switch.
• If the parameter does not change
Refer to Liftgate Close Switch Malfunction - DTC B396E B396E.
• If the parameter changes
15. Verify the liftgate will power close by pressing the pressing the liftgate close switch.
• If the liftgate does not power close
Refer to Liftgate Motor Power Open/Close Malfunction - DTC B396A B396A
• If the liftgate power closes
16. Verify the liftgate will power open by pressing the pressing the liftgate handle switch.
• If the liftgate does not power open
Refer to Liftgate Motor Power Open/Close Malfunction - DTC B396A B396A
• If the liftgate power opens
17. Verify the liftgate opens and closes smoothly without binding or mis-alignment
• If the liftgate binds or is mis-aligned
Refer to Liftgate Adjustment or Liftgate Lock Striker Adjustment Adjustments
• If the liftgate opens and closes smoothly without binding or mis-alignment
18. Verify the liftgate has not been auto reversing un-expectedly.
• If the liftgate has been auto reversing, inspect the following listed below:
Low pump fluid - refer to Liftgate Hydraulic System Refilling Liftgate Hydraulic System Refilling.
Pump actuator hoses for twists or kinks.
Fluid leaks.
Both liftgate object sensors for interference or deformity
• If the liftgate has not been auto reversing un-expectedly
19. All OK.