Inspection Procedure 14: ESS inoperative or improper operative.

caution

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 - CAN Bus Diagnostics Table ).
Whenever ECU is replaced, ensure that the CAN bus lines are normal.
When the hydraulic unit (integrated with ASTC-ECU) is replaced, always carry out the calibration of the master cylinder pressure sensor, steering wheel sensor and the G and yaw rate sensor (Refer to ).

COMMENTS ON TROUBLE SYMPTOM

Because the ASTC system has set the diagnosis code, the emergency brake signal system (ESS) may be disabled.

PROBABLE CAUSES

Low battery voltage
The CAN bus line is defective.
The ASTC-ECU, which was used on another vehicle, is installed on this vehicle.
The ETACS-ECU, which was used on another vehicle, is installed on this vehicle.
Wrong coding which the ETACS-ECU has stored.
ETACS-ECU malfunction
Damaged harness wires and connectors
Malfunction of the hydraulic unit assembly (integrated with ASTC-ECU)

DIAGNOSIS PROCEDURE

STEP 1. Check the part number of the hydraulic unit assembly (integrated with ASTC-ECU).

Check the part number of the hydraulic unit assembly (integrated with ASTC-ECU).

Q. Is the check result normal?

	Go to Step 2.

	Replace the hydraulic unit assembly (integrated with ASTC-ECU) (Refer to ). Then go to Step 2.

STEP 2. Check part number of ETACS-ECU

Check the part number of ETACS-ECU.

Q. Is the check result normal?

	Go to Step 3.

	Replace ETACS-ECU. (Refer to GROUP 54A - ETACS-ECU .) Then go to Step 3.

STEP 3. Check the diagnosis code.

Use the M.U.T.-III to check whether the ASTC system (Refer to

) and the ETACS-ECU set a diagnosis code (Refer to GROUP 54A - ETACS, Diagnosis Code Chart

Q. Is the check result normal?

	Go to Step 4.

	Diagnose the system according to the relevant diagnosis code procedure, and then go to Step 8.

STEP 4. M.U.T.-III actuator test

Perform the actuator test below to function-check the emergency braking signal system (Refer to

Item No. 10: ESS test mode

Q. Is the check result normal?

	This diagnosis is complete.

	Go to Step 5.

STEP 5. ETACS-ECU coding data check

Using M.U.T.-III, check if any abnormality is present in the coding data below which is stored in the ETACS-ECU.

ESS
OK: Available

Q. Is the check result normal?

	Go to Step 6.

	Replace ETACS-ECU. (Refer to GROUP 54A - ETACS-ECU .) Then go to Step 9.

STEP 6. Check the ASTC-ECU power supply circuit.

Refer to

Q. Is the check result normal?

	Go to Step 7.

	Diagnose the power supply circuit to the ASTC-ECU (Refer to ). Then go to Step 9.

STEP 7. M.U.T.-III actuator test

Perform the actuator test below to function-check the emergency braking signal system (Refer to

Item No. 10: ESS test mode

Q. Is the check result normal?

	This diagnosis is complete.

	Replace ETACS-ECU. (Refer to GROUP 54A - ETACS-ECU .) Then go to Step 9.

STEP 8. M.U.T.-III actuator test

Perform the actuator test below to function-check the emergency braking signal system (Refer to

Item No. 10: ESS test mode

Q. Is the check result normal?

	This diagnosis is complete.

	Replace the hydraulic unit assembly (integrated with ASTC-ECU) (Refer to ). Then go to Step 9.

STEP 9. M.U.T.-III actuator test

Perform the actuator test below to function-check the emergency braking signal system (Refer to

Item No. 10: ESS test mode

Q. Is the check result normal?

	This diagnosis is complete.

	Return to Step 1.