Inspection Procedure 2: Mode Does Not Change Even When the AWC Switch Is Pressed

INSPECTION PROCEDURE 2: Mode does not change even when the AWC switch is pressed





CAUTION:
^ If there is any problem in the CAN bus lines, an incorrect trouble symptom may occur. Prior to this diagnosis, always diagnose the CAN bus lines.
^ Whenever the ECU is replaced, ensure that the CAN bus lines are normal.

COMMENTS ON TROUBLE SYMPTOM
AWC switch or AWC-ECU may have a problem.

PROBABLE CAUSES
^ AWC switch malfunction
^ Malfunction of the ETACS-ECU
^ Malfunction of the combination meter
^ Damaged harness wires and connectors
^ Malfunction of AWC-ECU

DIAGNOSTIC PROCEDURE

STEP 1. Scan tool CAN bus diagnostics
Using scan tool MB991958, diagnose the CAN bus lines.

Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the CAN bus lines. After repairing the CAN bus line, go to Step 2.

STEP 2. Retest the system.

Q: Is the check result normal?
YES: Intermittent malfunction. (Refer to How to Cope with Intermittent Malfunction).
NO: Go to Step 3.

STEP 3. Scan tool data list
Item No.89: AWC switch.

Q: Is the check result normal?
YES: Go to Step 11.
NO: Go to Step 4.

STEP 4. AWC switch check.
Check the AWC switch.

Q: Is the check result normal?
YES: Go to Step 5.
NO: Replace the AWC switch. Then go to Step 13.

STEP 5. Measure the voltage at C-50 AWC switch connector.
1) Disconnect the connector, and measure the voltage between terminal No.2 and ground at the harness side.
2) Turn the ignition switch to the "ON" position.
OK: Battery positive voltage

Q: Is the check result normal?
YES: Go to Step 8.
NO: Go to Step 6.

STEP 6. AWC switch connector, ETACS-ECU connector check: C50, C-317

Q: Is the check result normal?
YES: Go to Step 7.
NO: Repair the defective connector. Then go to Step 13.

STEP 7. Check the wiring harness between C-50 AWC switch connector terminal No.2 and C-317 ETACS-ECU connector terminal No.5.
Check the power supply line for short or open circuit.

Q: Is the check result normal?
YES: Replace the ETACS-ECU. Then go to Step 12.
NO: Repair the wiring harness. Then go to Step 13.

STEP 8. Voltage measurement at C-51 AWC-ECU connector
1) With C-51 AWC-ECU connector connected, measure the voltage between terminal No.21 and ground at the harness side.
2) Turn the ignition switch to the "ON" position.
OK: Battery voltage (Press and hold the AWC switch) OK: 1 V or less (Release the AWC switch)

Q: Is the check result normal?
YES: Go to Step 11.
NO: Go to Step 9.

STEP 9. Intermediate connector, AWC-ECU connector, AWC switch connector check: C-36, C-51, C-50

Q: Is the check result normal?
YES: Go to Step 10.
NO: Repair the defective connector. Then go to Step 13.

STEP 10. Wiring harness check between C-51 AWC-ECU connector terminal No.21 and C-50 AWC switch connector terminal No.1
Check the output line for short or open circuit.

Q: Is the check result normal?
YES: Go to Step 12.
NO: Repair the wiring harness. Then go to Step 11.

STEP 11. Scan tool data list
Combination meter item No.F13, F14, F15: Mode display.

Q: Is the check result normal?
YES: Go to Step 12.
NO: Replace the combination meter. Then go to Step 12.

STEP 12. Retest the system.

Q: Is the check result normal?
YES: Intermittent malfunction. (Refer to How to Cope with Intermittent Malfunction).
NO: Replace the AWC-ECU. Then go to Step 13.

STEP 13. Retest the system.

Q: Is the check result normal?
YES: Return to Step 1.
NO: This diagnosis is complete.