STEP 1. Check the vehicle communication interface (V.C.I.) MB991824 operations.
STEP 2. Check the battery.
STEP 3. Check harness connector C-227 at data link connector for damage.
STEP 4. Measure the power supply voltage at data link connector harness side connector C-227.
STEP 5. Check harness connector C-417 at ETACS-ECU for damage.
STEP 6. Check for open circuit and short circuit to ground between ETACS-ECU connector C-417 (terminal No. 8) and data link connector C-227 (terminal No. 16).
STEP 7. Check harness connector C-408 at ETACS-ECU for damage.
STEP 8. Check for open circuit and short circuit to ground between battery and ETACS-ECU connector C-408 (terminal No. 1).
Is the harness wire in good condition?
Check No. 5 fuse in the ETACS-ECU, and replace as required. If the fuse is in good condition, replace the ETACS-ECU. Then confirm that the malfunction symptom is eliminated. Repair it. Then confirm that the malfunction symptom is eliminated.
STEP 9. Check the continuity at data link connector harness side connector C-227.
STEP 10. Check harness connector C-408 and C-417 at ETACS-ECU for damage.
STEP 11. Check the continuity at ETACS-ECU connectors C-408 and C-417.
(1) Disconnect the connectors C-408, C-417 and measure at the ETACS-ECU side.
(2) Check for the continuity between terminal No. 1 (C-408) and terminal No. 8 (C-417). Does continuity exist?
Go to Step 12. Check No. 5 fuse in the ETACS-ECU, and replace as required. If the fuse is in good condition, replace the ETACS-ECU. Then confirm that the malfunction symptom is eliminated.
STEP 12. Check for harness damage between battery and ETACS-ECU connector C-408 (terminal No. 1).
STEP 13. Check for harness damage between ETACS-ECU connector C-417 (terminal No. 8) and data link connector C-227 (terminal No. 16).
Is the harness wire in good condition?
Refer to the scan tool MB991958 reference manual. Repair it. Then confirm that the malfunction symptom is eliminated.
STEP 14. Using scan tool MB991958, diagnose CAN bus line.
(1) Turn the ignition switch to the "ON" position.
(2) Diagnose CAN bus line.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Is the CAN bus line normal?
Refer to, Inspection Procedure 23 - Power Supply System and Ignition Switch-IG System . Repair the CAN bus line. Refer to GROUP 54C, Diagnosis - CAN Bus Diagnostics Table . Then confirm that the malfunction symptom is eliminated.