For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | 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 | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Liftgate Position Sensor 5 V Reference Voltage | B153E 08 | 2 | 2 | --
Liftgate Disable Signal | 1, 2 | 1 | 1 | --
Liftgate Open Signal - Exterior Switch | B396E 02 | 1 | 1 | --
Liftgate Open Signal - Shut Face Switch | B396E 02 | 1 | 1 | --
Object Sensors Signal | B153F 02 | B153F 05 | B153F 05 | B153F 03, B153F 07
Liftgate Open Signal - Exterior Switch | B396E 02 | 1 | 1 | --
Open/Close Switches Signal | B396D 02 | 1, 2 | 1, 2 | --
Pawl Switch Signal | B153A 08 | B153A 08 | B153A 08 | B153A 08
Position Sensor Signal 1 | B153E 08 | B153E 08 | B153E 08 | B153E 08
Position Sensor Signal 2 | B153E 08 | B153E 08 | B153E 08 | B153E 08
Ratchet Switch Signal | B153A 08 | B153A 08 | B153A 08 | B153A 08
Sector Switch Signal | B153A 08 | B153A 08 | B153A 08 | B153A 08
Liftgate Latch Cinch Control | B2495 02 | B2495 04 | B2495 01 | --
Liftgate Latch Release Control | B2495 02 | B2495 04 | B2495 01 | --
Liftgate Motor Close Control | B396A 02 | B396A 04 | B396A 01 | --
Liftgate Motor Open Control | B396A 02 | B396A 04 | B396A 01 | --
Liftgate Switches Low Reference | -- | B153A 08 | 1 | B153E 08
Position Sensor Low Reference | -- | B0153E 08 | 2 | --
Mode/Release Switch Ground | -- | 1 | 1 | --
Liftgate Control Module Ground | -- | U0230 00 | 2 | --
1. Liftgate Switch Malfunction 2. Liftgate Malfunction

### Circuit/System Description

The liftgate control module controls operation of the liftgate latch motor and the liftgate actuator assembly. Under normal conditions the power latch can only be unlatched under power from the liftgate control module through an input from the liftgate handle switch, the instrument panel switch, or the remote keyless entry transmitter, but the liftgate may be manually closed to the primary latched position without the liftgate control module performing the power latch function. The ON/OFF switch in the instrument panel switch bank will enable or disable the power open/close operation of the actuator assembly but will have no effect on power latch operation. The liftgate actuator assembly consists of the actuator drive motor with 2 internal Hall effect sensors. The drive motor is mated to a worm type gear off the actuator clutch and when the clutch is engaged the motor rotation is transferred to the clutch gear, intermediate gear, and actuator arm gear. The full open switch is a limit switch mounted on the liftgate actuator assembly along side the actuator arm gear, and will make contact with the cam on the actuator arm gear when the liftgate is near the full open position. The liftgate control module continuously monitors the liftgate location and direction of travel using the 2 Hall effect sensors in the drive motor. The sensor counts are used to determine when the liftgate has reached the open and closed points of travel where the actuator clutch should be disengaged. These positions may vary slightly and must be learned when most liftgate components are serviced.

### Diagnostic Aids

Note: Before testing can be performed the liftgate must be opened. Refer to Opening the Liftgate Without Electrical Power for the appropriate procedure.

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:

• | After a power loss of the low current battery supply until the ignition is cycled.

• | Vehicle is not in park.

• | Engine cranking is present.

• | Ambient temperature at the liftgate control module must be within -17 to +80°C (+1 to +176°F).

• | Liftgate motor excess current is detected.

• | System voltage is out of range.

• | A DTC is set that disables power liftgate functionality.

• | The liftgate is locked when attempting to open from exterior handle.

The liftgate control module also receives input from 2 pressure sensing object detection sensors. If either of these sensors indicates an object may be pinched as the liftgate is brought to the closed position, the liftgate will reverse direction and power close operation will be suspended until the pressure against the sensor is released.

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.

Certain SIR DTCs will make the power liftgate inoperative. Correct any SIR concern first before performing any extensive power liftgate diagnostics.

### Reference Information

#### Schematic Reference

Liftgate Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Rear Hatch/Gate Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the scan tool Door/Liftgate Locked Switch parameter while pressing and depressing the Liftgate Enable/Disable button on the inside switch assembly. The parameter should change from Inactive to Active.

⇒ | If the parameter does not change, refer to Mode/Release Switch Inoperative.

2. Observe the scan tool Liftgate Front Control Switch parameter while pressing and releasing the liftgate button on the inside switch assembly. The parameter should change from Inactive and Active.

⇒ | If the parameter does not change, refer to Mode/Release Switch Inoperative.

3. Observe the Liftgate Handle Switch Status parameter while pressing and releasing the touchpad on the liftgate handle, the parameter should change from Inactive and Active.

⇒ | If the parameter does not change, refer to Liftgate Handle Switch Inoperative.

4. Disable the power liftgate by pressing the Liftgate Enable/Disable button on the inside switch assembly and manually open and close the liftgate. The liftgate should release, open and close manually, cinch-in and latch.

⇒ | If the liftgate fails to release, cinch-in or latch, refer to Latch Assembly Malfunction.

5. Manually open the liftgate and verify that the liftgate will remain at or near the full open position for several minutes.

⇒ | If the liftgate will not remain open, replace the liftgate struts.

6. Command the liftgate to Open and Close with a scan tool. The liftgate should Open and Close as commanded.

⇒ | If the liftgate fails to Open and Close, refer to Power Liftgate Inoperative.

⇒ | If the liftgate closes and immediately reopens, refer to Liftgate Closes and Reopens.

### Circuit/System Testing

#### Mode/Release Switch Inoperative

1. Ignition OFF, disconnect the harness connector at the S58B Rear Compartment Lid Unlatch Switch - Interior.
2. Test for less than 1 Ω between the ground circuit terminal 1 and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Door/Liftgate Locked Switch parameter is Inactive.

⇒ | If not the specified parameter, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the K39 Liftgate Control Module.

4. Verify the scan tool Liftgate Front Control Switch parameter is Inactive.

⇒ | If not the specified parameter, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K39 Liftgate Control Module.

5. Install a 3 A fused jumper wire between the signal circuit terminal 3 and ground. Verify the scan tool Door/Liftgate Locked Switch parameter is Active.

⇒ | If not the specified parameter, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

6. Install a 3 A fused jumper wire between the signal circuit terminal 4 and ground. Verify the scan tool Liftgate Front Control Switch parameter is Active.

⇒ | If not the specified parameter, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

7. If all circuits test normal, test or replace the inside switch assembly.

#### Liftgate Handle Switch Inoperative

1. Ignition OFF, disconnect the harness connectors at the S58A Rear Compartment Lid Unlatch Switch - Exterior and S45B Liftgate Control Switch - Interior.
2. Ignition ON, verify the scan tool Liftgate Handle Switch Status parameter is Inactive.

⇒ | If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the K39 Liftgate Control Module.

3. Ignition OFF, connect the harness connector at the S58A Rear Compartment Lid Unlatch Switch - Exterior.
4. Ignition ON, observe the scan tool Liftgate Handle Switch Status parameter while pressing and releasing the S58A Rear Compartment Lid Unlatch Switch - Exterior, the parameter should change between Active and Inactive.

⇒ | If the parameter does not change, test or replace the S58A Rear Compartment Lid Unlatch Switch - Exterior.

5. If all circuits test normal, test or replace the S45B Liftgate Control Switch - Interior.

#### Latch Assembly Malfunction

1. Ignition OFF, disconnect the harness connector at the M31 Liftgate Latch Assembly.
2. Ignition OFF, test for less than 1 Ω between the control circuit terminal 1 and ground.

⇒ | If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuits test normal, replace the K39 Liftgate Control Module.

3. Ignition OFF, test for less than 1 Ω between the control circuit terminal 3 and ground.

⇒ | If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuits test normal, replace the K39 Liftgate Control Module.

4. Connect a test lamp between control circuit terminal 1 and control circuit terminal 3.
5. Command the liftgate to Open and Close with a scan tool. The test lamp should turn ON when commanding the Open and Close states.

⇒ | If the test lamp remains OFF during either of the commands, test for a short to ground on both control circuits. If the circuits test normal, replace the K39 Liftgate Control Module.

6. Ignition OFF, test for less than 1 Ω between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

7. Ignition ON, verify the scan tool Liftgate Latch Pawl Switch parameter is Inactive

⇒ | If not the specified parameter, test the signal circuit terminal 5 for a short to ground. If the circuit tests normal, replace the K39 Liftgate Control Module.

8. Verify the scan tool Liftgate Latch Ratchet Switch parameter is Inactive

⇒ | If not the specified parameter, test the signal circuit terminal 6 for a short to ground. If the circuit tests normal, replace the K39 Liftgate Control Module.

9. Verify the scan tool Liftgate Latch Sector Switch parameter is Inactive.

⇒ | If not the specified parameter, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K39 Liftgate Control Module.

10. Install a 3 A fused jumper wire between the signal circuit terminal 5 and low reference circuit terminal 2. Verify the scan tool Liftgate Latch Pawl Switch parameter is Active.

⇒ | If not the specified parameter, test the signal circuit terminal 5 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

11. Install a 3 A fused jumper wire between the signal circuit terminal 6 and low reference circuit terminal 2. Verify the scan tool Liftgate Latch Ratchet Switch parameter is Active.

⇒ | If not the specified parameter, test the signal circuit terminal 6 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

12. Install a 3 A fused jumper wire between the signal circuit terminal 4 and low reference circuit terminal 2. Verify the scan tool Liftgate Latch Sector Switch parameter is Active.

⇒ | If not the specified parameter, test the signal circuit terminal 4 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

13. If all circuits test normal, test or replace the M31 Liftgate Latch Assembly.

#### Power Liftgate Inoperative

1. Ignition OFF, disconnect the X2 harness connector at the K39 Liftgate Control Module.
2. Test for less than 1 Ω between the ground terminal F and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal M and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the fuse is open, replace the K39 Liftgate Control Module.

#### Liftgate Closes and Reopens

Note: Check the alignment of the liftgate striker, if the liftgate striker is adjusted too far inboard it could allow the liftgate control module to detect an excess motor current condition and reverse the motor.

1. Ignition OFF, disconnect the X1 harness connector at the K39 Liftgate Control Module.
2. Test for infinite resistance between the signal circuit terminal M and ground.

⇒ | If less than the specified value, test the signal circuit for a short to ground.

3. Test for 15K - 25K Ω between the signal circuit terminal M and the low reference circuit terminal L.

⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

⇒ | If not within the specified range, test the signal circuit between the B71L Liftgate Object Sensor - Left or B71R Liftgate Object Sensor - Right. and the low reference circuit for an open/high resistance. If the circuits test normal, test or replace the B71L Liftgate Object Sensor - Left or B71R Liftgate Object Sensor - Right.

4. If all circuits test normal, replace the K39 Liftgate Control Module.

### Component Testing

#### Liftgate Object Sensor

1. Ignition OFF, disconnect the harness connector at the B71R Liftgate Object Sensor - Right.
2. Test for 10K Ω between the signal terminal A and the low reference terminal B.

⇒ | If not within the specified range, replace the B71R Liftgate Object Sensor - Right.

3. Disconnect the harness connector at the B71L Liftgate Object Sensor - Left.
4. Test for 10K Ω between the signal terminal A and the low reference terminal B.

⇒ | If resistance is not within the specified range, replace the B71L Liftgate Object Sensor - Left.

#### Liftgate Exterior Switch

1. Ignition OFF, disconnect the harness connector at the S58A Rear Compartment Lid Unlatch Switch - Exterior.
2. Test for infinite resistance between the signal terminal 1 and the low reference terminal 2 with the switch in the open position.

⇒ | If not the specified value, replace the S58A Rear Compartment Lid Unlatch Switch - Exterior.

3. Test for less than 2 Ω between the signal terminal 1 and the low reference terminal 2 with the switch in the closed position.

⇒ | If greater than the specified range, replace the S58A Rear Compartment Lid Unlatch Switch - Exterior.

#### Liftgate Interior Switch

1. Ignition OFF, disconnect the harness connector at the S45B Liftgate Control Switch - Interior.
2. Test for infinite resistance between the signal terminal 3 and the low reference terminal 4 with the switch in the open position.

⇒ | If not the specified value, replace the S45B Liftgate Control Switch - Interior.

3. Test for less than 2 Ω between the signal terminal 3 and the low reference terminal 4 with the switch in the closed position.

⇒ | If greater than the specified range, replace the S45B Liftgate Control Switch - Interior.

#### Liftgate Latch Assembly

1. Install a 20 A fused jumper wire between the control terminal 1 and 12 V. Momentarily install a jumper wire between the control terminal 3 and ground. The liftgate latch assembly should perform the Cinch or Release function.

⇒ | If the function does not perform as specified, replace the liftgate latch assembly.

2. Reverse the jumper wires, the liftgate latch assembly should perform the Release or Cinch function.

⇒ | If the function does not perform as specified, replace the A23C Door Latch Assembly - Liftgate.

#### Mode/Release Switch Assembly

1. Ignition OFF, disconnect the harness connector at the S58B Rear Compartment Lid Unlatch Switch - Interior.
2. Test for infinite resistance between the signal terminal 4 and the ground terminal 1 with the liftgate open switch in the inactive position.

⇒ | If not the specified value, replace the S58B Rear Compartment Lid Unlatch Switch - Interior.

3. Test for infinite resistance between the signal terminal 3 and the ground terminal 1 with the liftgate disable switch in the inactive position.

⇒ | If not the specified value, replace the S58B Rear Compartment Lid Unlatch Switch - Interior.

4. Test for less than 3 Ω between the signal terminal 4 and the ground terminal 1 with the liftgate open switch in the active position.

⇒ | If greater than the specified range, replace the S58B Rear Compartment Lid Unlatch Switch - Interior.

5. Test for less than 3 Ω between the signal terminal 3 and the ground terminal 1 with the liftgate disable switch in the enable position.

⇒ | If greater than the specified range, replace the S58B Rear Compartment Lid Unlatch Switch - Interior.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Liftgate Release Switch Replacement

• | Liftgate Latch Replacement

• | Liftgate Outside Handle Replacement

• | Liftgate Side Upper Sensor Replacement

• | Control Module References for liftgate control module replacement, setup and programming