Diagnostic Procedure

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

Q: Is the check result normal?
1. YES: Go to Step 3.
2. 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?
1. YES: Intermittent malfunction. (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION .)
2. NO: Go to Step 3.
STEP 3. Scan tool service data
Item No. 89: AWC switch (Refer to SERVICE DATA REFERENCE TABLE .)

Q: Is the check result normal?
1. YES: Go to Step 11.
2. 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?
1. YES: Go to Step 5.
2. NO: Replace the AWC switch. (Refer to AWC-ECU .) Then go to Step 13.
STEP 5. Measure the voltage at C-120 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?
1. YES: Go to Step 8.
2. NO: Go to Step 6.
STEP 6. AWC switch connector, ETACS-ECU connector, J/C (1) check: C-120, C-317, C-101
Q: Is the check result normal?
1. YES: Go to Step 7.
2. NO: Repair the defective connector. Then go to Step 13.
STEP 7. Check the wiring harness between C-120 AWC switch connector terminal No. 2 and C-317 ETACS-ECU connector terminal No. 5.
Check the wiring harness for open or short circuit (short to ground).

Q: Is the check result normal?
1. YES: Replace the ETACS-ECU. (Refer to ETACS-ECU .) Then go to Step 12.
2. NO: Repair the wiring harness. Then go to Step 13.
STEP 8. Voltage measurement at C-46 AWC-ECU connector
1. With C-46 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?
1. YES: Go to Step 11.
2. NO: Go to Step 9.
STEP 9. Intermediate connector, AWC-ECU connector, AWC switch connector check: C-42, C-46, C-120
Q: Is the check result normal?
1. YES: Go to Step 10.
2. NO: Repair the defective connector. Then go to Step 13.
STEP 10. Wiring harness check between C-46 AWC-ECU connector terminal No. 21 and C-120 AWC switch connector terminal No. 1
Check the wiring harness for open or short circuit (short to ground).

Q: Is the check result normal?
1. YES: Replace the AWC-ECU. (Refer to AWC-ECU .) Then go to Step 13.
2. NO: Repair the wiring harness. Then go to Step 11.
STEP 11. Scan tool service data
Combination meter item No. F13, F14, F15: Mode display (Refer to SERVICE DATA .)

Q: Is the check result normal?
1. YES: Go to Step 12.
2. 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?
1. YES: Intermittent malfunction. (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION .)
2. 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?
1. YES: Return to Step 1.
2. NO: This diagnosis is complete.