Before replacing the ECU,
ensure that the communication circuit is normal.
OPERATION
The ASC-ECU illuminates the stop lamp while the ACC or the FCM is braking the vehicle
automatically. The ASC-ECU monitors whether the stop lamps illuminate or go out.
DIAGNOSIS CODE SET CONDITIONS
The ASC-ECU stores the diagnosis code when it detects a malfunction during monitoring.
PROBABLE CAUSES
Damaged wiring harness and connectors
Malfunction of ASC-ECU
DIAGNOSIS PROCEDURE
STEP 1. Check the stop lamp switch.
The stop lamps should illuminate when the brake pedal is depressed.
Q.
Is the check result normal?
Go to Step 2
Carry out troubleshooting for the stop lamps. Refer to GROUP 54A - Rear
Combination Lamp .
STEP 2. M.U.T.-III actuator test
When the actuator test is performed, the stop lamps should illuminate.
Item 11: Stop lamp:ON (Refer to ).
Q.
Is the check result normal?
Go to Step 4
Go to Step 3
STEP 3. Check of short to power supply, short to earth, and open circuit
in STLD line between ASC-ECU connector and ETACS-ECU connector
Q.
Is the check result normal?
Go to Step 4
Repair the connector(s) or wiring harness. Then go to Step 6.
STEP 4. Check of short to power supply, short to earth, and open circuit
in STP line between ASC-ECU connector and stop lamp connector
Q.
Is the check result normal?
Go to Step 5
Repair the connector(s) or wiring harness. Then go to Step 6.
STEP 5. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Ignition switch "LOCK" (OFF)
(3)Ignition switch "ON"
Q.
Is diagnosis code No.C1801 set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ).
Then go to Step 6.
This diagnosis is complete.
STEP 6. Check whether the diagnosis code is reset.
Go to Step 2
Carry out troubleshooting for the stop lamps. Refer to GROUP 54A - Rear
Combination Lamp 
.