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Inspection Procedure 1: Scan tool (M.U.T.-IIISE) communication with FCM/LDW/AHB system is impossible.
 
 
caution
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.
 
 
COMMENTS ON TROUBLE SYMPTOM
When scan tool (M.U.T.-IIISE) cannot communicate with the FCM/LDW/AHB system, the CAN bus lines, FCM/LDW/AHB-ECU power supply circuit system, ground, or FCM/LDW/AHB-ECU may be faulty.
 
 
TROUBLESHOOTING HINTS
  • Malfunction of the FCM/LDW/AHB-ECU power supply circuit
  • Malfunction of the FCM/LDW/AHB-ECU
 
 
DIAGNOSIS
Required Special Tools:
  • MB991223: Harness Set
  • MB992006: Extra Fine Probe
STEP 1. Resistance measurement at FCM/LDW/AHB-ECU connector (GND terminal).
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Measure the resistance between the FCM/LDW/AHB-ECU connector (GND terminal) and body ground.
OK: Is the measured resistance 2 ohms or less
Is the check result normal?
Go to Step 3.
Go to Step 2.
 
STEP 2. Check of open circuit in GND line between FCM/LDW/AHB-ECU connector and body ground.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.
 
STEP 3. Voltage measurement at FCM/LDW/AHB-ECU connector (IG terminal).
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3) Check the voltage between the FCM/LDW/AHB-ECU connector (IG terminal) and body ground.
OK: Is the measured voltage approximately 12 volts (battery positive voltage)
Is the check result normal?
Go to Step 4.
Go to Step 5.
 
STEP 4. Retest the system.
Can scan tool (M.U.T.-IIISE) communicate with a FCM/LDW/AHB system?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Replace the FCM/LDW/AHB-ECU (Refer to ).
 
STEP 5. Check of short to ground, and open circuit in IG line between fusible link and FCM/LDW/AHB-ECU connector.
Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).
Repair the connector(s) or wiring harness.