Inspection Procedure
1: Cannot communicate with LDW-ECU using the M.U.T.-III.
caution
When replacing the ECU, always
check that the communication circuit is normal.
COMMENTS ON TROUBLE SYMPTOM
LDW-ECU is communicating with M.U.T.-III via CAN. Therefore, communication error of LDW-ECU
is suspected.
PROBABLE CAUSES
Malfunction of the power supply and the earth of LDW-ECU
Malfunction of CAN bus line
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics
Use M.U.T.-III to diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 2
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ).
STEP 2. Voltage measurement at LDW-ECU connector (IG terminal).
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Check the voltage between the LDW-ECU connector (IG terminal) and body earth. OK: System voltage
Q.
Is the check result normal?
Go to Step 3.
Repair the power supply circuit to LDW-ECU.
STEP 3. Resistance measurement at LDW-ECU connector (GND terminal)
(1)Disconnect the connector, and measure at the wiring harness side.
(2)Measure the resistance between the LDW-ECU connector (GND terminal) and body earth. OK: Continuity exists (2 Ω or less)
Q.
Is the check result normal?
Go to Step 5.
Go to Step 4.
STEP 4. Check of open circuit in GND line between LDW-ECU connector
and body earth.
Q.
Is the check result normal?
Go to Step 5.
Repair the earth circuit to LDW-ECU.
STEP 5. Retest the system
Check if M.U.T.-III can communicate with LDW-ECU.
Q.
Is the check result normal?
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection
Service Points - How to cope with Intermittent Malfunction ).
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting 
).