Liftgate Release Inoperative (w/o E61)
Liftgate Release Inoperative (w/o E61)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The liftgate release switch is an input to the body control module (BCM). The BCM supplies battery voltage to the signal circuit and when the release switch is activated the signal circuit voltage goes low. The BCM controls the liftgate release actuator through the liftgate latch release relay. When the release switch signal is activated, the BCM enables the liftgate latch release relay by applying battery voltage to the liftgate latch release relay supply circuit and the relay is energized when the BCM grounds the liftgate latch release relay control circuit. When the relay is energized battery voltage is supplied to the liftgate release actuator through the liftgate release actuator control circuit.
Diagnostic Aids
Before some testing can be performed the liftgate must be opened. Refer to Opening the Liftgate Without Electrical Power.
Circuit/System Verification
1. Install a scan tool and display Liftgate Release Switch parameter in the BCM Inputs data list.
2. Ignition ON, the parameter should be active only when the release switch is activated.
3. Observe the scan tool Liftgate Release Switch parameter while pressing and releasing the liftgate handle switch. The reading should change between Active and Inactive.
^ If not the specified value, refer to the Liftgate Release Switch Circuit Test.
4. Connect a test lamp between the relay side of LIFTGATE RELSE fuse and ground.
5. Command the Liftgate Release Actuator ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
^ If the test lamp does not turn on and off while changing between the commanded states, refer to the Liftgate Release Relay Control Circuit Test.
6. If the liftgate release actuator cannot be activated using the scan tool output controls function, refer to the Liftgate Release Actuator Circuit Test.
Circuit/System Testing
Liftgate Release Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the liftgate handle switch.
2. Test for less than 1.0 ohm of resistance between the ground circuit terminal B and ground.
^ If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Liftgate Release Switch parameter is Inactive.
^ If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM.
4. Install a 3A fused jumper wire between the signal circuit terminal A and the ground circuit terminal B. Verify the scan tool Liftgate Release Switch parameter is Active.
^ If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If the release switch circuits test normal, replace the liftgate handle switch.
Liftgate Release Relay Control Circuit Test
1. Ignition OFF, disconnect the X7 harness connector at the BCM.
2. Install a 10A fused jumper wire between the B+ circuit terminal 3 and B+. Verify the release actuator does not activate.
^ If the release actuator activates, test the control circuit terminal 1 for a short to ground. If the circuit tests normal replace the underhood fuse block.
^ If the fuse in the jumper wire opens, test the B+ circuit terminal 3 for a short to ground. If the circuit tests normal replace the underhood fuse block.
3. Briefly install another 10A fused jumper wire between the relay control circuit terminal 1 and ground. Verify the release actuator activates.
^ If the release actuator does not activate, test the relay control circuit for an open/high resistance. If the circuit tests normal replace the underhood fuse block.
4. If all circuits test normal, replace the BCM.
Liftgate Release Actuator Circuit Test
1. Ignition OFF, disconnect the harness connector at the liftgate latch.
2. Test for less than 1.0 ohm of resistance between the ground circuit terminal 3 and ground.
^ If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal 1 and the ground circuit terminal 3.
4. Command the Liftgate Release Actuator ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
^ If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
^ If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the liftgate latch.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Liftgate Release Switch Replacement (Except Avalanche and EXT Escalade)