If there is any
problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis,
diagnose the CAN bus lines (Refer to GROUP 54C - Troubleshooting ).
Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
When the ACC/FCM-ECU is replaced, calibrate the radar (refer to ).
OPERATION
The ACC/FCM-ECU receives the FCM and UMS ON/OFF switch signal from the ASTC-ECU
via CAN communication.
DIAGNOSIS CODE SET CONDITION
This diagnosis code is set when the abnormality below is detected:
The FCM and UMS ON/OFF switch remains on for at least one minute.
PROBABLE CAUSES
Malfunction of the CAN bus line
Malfunction of the hydraulic unit assembly (integrated with ASTC-ECU)
Damaged wiring harness and connectors
Malfunction of the FCM and UMS ON/OFF switch
Malfunction of the ACC/FCM-ECU
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnosis.
Use M.U.T.-III to perform the CAN bus diagnosis.
Q.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting ).
On completion, go to Step 2.
STEP 2. Use M.U.T.-III to confirm a diagnosis code of other systems.
Check if the diagnosis code is set in the ASTC-ECU.
Q.
Is the diagnosis code set?
Troubleshoot the ASTC-ECU diagnosis code (Refer to ).
Go to Step 3.
STEP 3. FCM and UMS ON/OFF switch check.
Check the FCM and UMS ON/OFF switch.
Q.
Is the check result normal?
Go to Step 4.
Replace the FCM and UMS ON/OFF switch.
STEP 4. Check of short circuit in FCSW line between ASTC-ECU connector
and FCM and UMS ON/OFF switch connector.
Q.
Is the check result normal?
Go to Step 5.
Repair the connector(s) or wiring harness.
STEP 5. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set in the ACC/FCM-ECU.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3)Start the engine.
(4)Press the FCM and UMS ON/OFF switch to turn the FCM system to ON.
(5)On completion, check that the diagnosis code is set again.
Q.
Is diagnosis code No. C1784 set?
Replace the ACC/FCM-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent
Malfunctions).