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Inspection procedure 1: Communication with ECM only is not possible
 
 
 
 
CIRCUIT OPERATION
  • Battery voltage is applied to the data link connector.
  • The data link connector is grounded to the vehicle body.
 
 
COMMENT
  • When the communication between M.U.T.-III and ECM is impossible, it can be suspected that the CAN bus line, power supply circuit of the data link connector, and/or grounding circuit are defective.
  • Communication can not be achieved either, if a wrong vehicle type is selected on M.U.T.-III.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this case: )
  • Battery failed.
  • Open or shorted data link connector circuit, harness damage or connector damage.
  • CAN communication failed.
  • Scan tool (M.U.T.-III) failed.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
  • 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 (Vehicles with CAN communication system)
STEP 1. Check the vehicle communication interface (V.C.I.) MB992744 or MB991824 operations.
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
(1) Connect scan tool (M.U.T-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) .
(2) When the power of V.C.I. is turned to ON, the indicator lamp of the V.C.I. illuminates in green.
  • The indicator lamp of the V.C.I. illuminates in green.
Is the indicator lamp of the V.C.I. illuminates in green?
Go to Step 6.
Go to Step 2.
 
STEP 2. Check the battery.
Refer to GROUP 54A, Battery - On-vehicle Service - Battery Test .
Are there any abnormalities?
Replace the battery. Then confirm that the malfunction symptom is eliminated.
Go to Step 3.
 
STEP 3. Measure the power supply voltage at data link connector harness side connector.
Measure voltage between terminal MUT line and ground.
  • Voltage should be battery positive voltage.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 4.
Repair or replace the connector(s), or check and repair the harness of open circuit, and short circuit in MUT line between data link connector and ETACS-ECU connector. Then confirm that the malfunction symptom is eliminated.
 
STEP 4. Check the continuity at data link connector harness side connector.
Check for the continuity between terminal ground line and ground.
  • Continuity (2 ohms or less)
Does continuity exist?
Go to Step 5.
Repair or replace the connector(s), or check and repair the harness of open circuit, and damage in ground line between data link connector and body ground. Then confirm that the malfunction symptom is eliminated.
 
STEP 5. Check of harness damage in MUT line between battery and data link connector.
Is the harness wire in good condition?
Refer to the scan tool (M.U.T.-III) reference manual.
Repair the connector(s) or wiring harness. Then confirm that the malfunction symptom is eliminated.
 
STEP 6. Using scan tool (M.U.T.-III), 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 - 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.