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. (Refer to TROUBLESHOOTING .) 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 service data
Item No. 90, 91: AWC switch (Refer to SERVICE DATA REFERENCE TABLE .)
Q: Is the check result normal?
YES : Go to Step 11.
NO : Go to Step 4.
- STEP 4. AWC switch single unit check
Check the AWC switch.(Refer to AWC SWITCH CHECK .)
Q: Is the check result normal?
YES : Go to Step 5.
NO : Replace the AWC switch.(Refer to AWC-ECU .) Then go to Step 13.
- STEP 5. Measure the voltage at C-214 AWC switch connector.
- Disconnect the connector, and measure the voltage between terminal No.2 and ground at the harness side.
- Turn the ignition switch to the "ON" position.
OK: Battery positive voltage
Q: Is the check result normal?
YES : Go to Step 9.
NO : Go to Step 6.
- STEP 6. Voltage measurement at C-46 AWC-ECU connector
- With C-46 AWC-ECU connector connected, measure the voltage between terminal No. 11 and ground at the harness side.
- Turn the ignition switch to the "ON" position.
OK: battery voltage
Q: Is the check result normal?
YES : Go to Step 7.
NO : Go to Step 12.
- STEP 7. AWC-ECU connector, intermediate connector, clock spring connector, AWC switch connector check: C-46, C-31, C-41, C-202, C-205, C-214
Q: Is the check result normal?
YES : Go to Step 8.
NO : Repair the defective connector. Then go to Step 13.
- STEP 8. Wiring harness check between C-46 AWC-ECU connector terminal No. 11 and C-214 AWC switch connector terminal No. 2
Check the wiring harness for open or short circuit (short to ground).
Q: Is the check result normal?
YES : Go to Step 12.
NO : Repair the wiring harness. Then go to Step 13.
- STEP 9. AWC-ECU connector, intermediate connector, clock spring connector, AWC switch connector check: C-46, C-31, C-41, C-202, C-205, C-214
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-46 AWC-ECU connector terminal No. 19 and C-214 AWC switch connector terminal No. 4
Check the wiring harness for open circuit.
Q: Is the check result normal?
YES : Go to Step 11.
NO : Repair the wiring harness. Then go to Step 13.
- STEP 11. Scan tool service data
Combination meter item No. F13, F14, F15: Mode display (Refer to COMBINATION METER .)
Q: Is the check result normal?
YES : Go to Step 12.
NO : Replace the combination meter. (Refer to 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.(Refer to 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.