Only Liftgate Lock Does Not Work

INSPECTION PROCEDURE: The Liftgate does not Open.

CAUTION:
Before replacing the ECU, ensure that the input and output signal circuits are normal.

OPERATION

The ETACS-ECU operates this function in accordance with the input signals shown below.

- Vehicle speed signal (ASC-ECU)
- Liftgate lock release handle
- Liftgate lock actuator

COMMENTS ON TROUBLE SYMPTOM

If this function does not work normally, a malfunction of the input signal circuit(s) mentioned above or ETACS-ECU is suspected.

PROBABLE CAUSES

- Vehicle speed signal (ASC-ECU) error
- Malfunction of the liftgate lock release handle
- Malfunction of the liftgate lock actuator
- Malfunction of ETACS-ECU
- Damaged wiring harness and connectors

DIAGNOSTIC PROCEDURE

Required Special Tools:

- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicles Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Checking central door unlocking operation

Check that the central door locking system works normally.

Q. Is the check result normal?

YES Go to Step 2.
NO Refer to inspection procedure 1 "Central door locking system does not work at all Inspection Procedure 1."
STEP 2. Using scan tool MB991958, read the diagnostic trouble code.

(1)
CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

Connect scan tool MB991958. Reading and Clearing Diagnostic Trouble Codes."
(2)Turn the ignition switch to the "ON" position.
(3)Check that the ASC-ECU sets a diagnostic trouble code.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC set?

YES Diagnose ASC-ECU Active Stability Control System (ASC)).

NO Go to Step 3.

STEP 3. Using scan tool MB991958, check data list.

Check the input signals from the liftgate lock release handle.

(4)Turn the ignition switch to the "LOCK" (OFF) position.
OK: Normal condition is displayed.

Q. Is the check result normal?

YES Go to Step 4.

NO Refer to inspection procedure: "The liftgate lock release handle signal is not received Liftgate Lock Release Handle Signal Is Not Received."

STEP 4. Check liftgate lock actuator connector F-38 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is liftgate lock actuator connector F-38 in good condition?

YES Go to Step 5.
NO Repair or replace the damaged component(s). Harness Connector Inspection. Verify that the liftgate can be locked and unlocked normally.
STEP 5. Check the liftgate lock actuator.

Remove the liftgate lock actuator. The illustration shows when the liftgate lock actuator is viewed from inside the liftgate. Refer to Liftgate Handle and Latch Service and Repair.

Q. Is the liftgate lock actuator normal?

YES Go to Step 6.

NO Replace the liftgate lock actuator. Verify that the liftgate can be locked and unlocked normally.

STEP 6. Check the ground circuit to the liftgate lock actuator. Measure the resistance at liftgate lock actuator connector F-38.

(1)Disconnect liftgate lock actuator connector F-38 and measure the resistance on the wiring harness side of the connector.

(2)Measure the resistance value between terminal 2 and ground.

- The resistance should be 2 ohms or less.

Q. Is the measured resistance 2 ohms or less?

YES Go to Step 8.

NO Go to Step 7.

STEP 7. Check the wiring harness between liftgate lock actuator connector F-38 (terminal 2) and ground.

- Check the ground line for open circuit and short circuit.

NOTE:
Also check intermediate connector F-31 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector F-31 is damaged, repair or replace the damaged component(s) as described in Harness Connector Inspection Harness Connector Inspection.

Q. Is the wiring harness between liftgate lock actuator connector F-38 (terminal 2) and ground in good condition?

YES No action is necessary and testing is complete.
NO The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. Verify that the liftgate can be locked and unlocked normally.
STEP 8. Check ETACS-ECU connector C-311 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is ETACS-ECU connector C-311 in good condition?

YES Go to Step 9.
NO Repair or replace the damaged component(s). Harness Connector Inspection. Verify that the liftgate can be locked and unlocked normally.
STEP 9. Check the wiring harness between ETACS-ECU connector C-311 (terminal 1) and liftgate lock actuator connector F-38 (terminal 1).

- Check the power supply line for open circuit and short circuit.

NOTE:
Also check intermediate connectors D-14, F-30 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connectors D-14, F-30 is damaged, repair or replace the damaged component(s) as described in Harness Connector Inspection Harness Connector Inspection.

Q. Is the wiring harness between ETACS-ECU connector C-311 (terminal 1) and liftgate lock actuator connector F-38 (terminal 1) in good condition?

YES Go to Step 10.
NO The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. Verify that the liftgate can be locked and unlocked normally.
STEP 10. Retest the system.

Check that the liftgate can be locked and unlocked normally.

Q. Is the check result normal?

YES No action is necessary and testing is complete.
NO Replace the ETACS-ECU. Check that the liftgate can be locked and unlocked normally.