Code No.C1346: Abnormal stop lamp circuit <Vehicles with FCM-LS>

caution

When more than one stop lamp do not illuminate due to a blown bulb, this diagnosis code may be set. Diagnose the rear combination lamps (Refer to GROUP 54A - Rear Combination Lamp, Troubleshooting, The Stop Lamps do not Illuminate or go out Normally ).
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 ECU is replaced, ensure that the CAN bus lines are normal.
When the hydraulic unit assembly (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor and the G sensor (Refer to and ).

OPERATION

ASC-ECU monitors whether the stop lamp is ON or OFF.
The ASC-ECU activates the stop lamp relay to illuminate the stop lamps.
The ASC-ECU monitors the operating conditions of the stop lamp switch, the stop lamps and the stop lamp relay.

DIAGNOSIS CODE SET CONDITIONS

The system cannot recognise the operating condition of the stop lamps.
When the stop lamp relay is off, the ON/OFF status of the stop lamp switch does not coincide with the actual stop lamp illumination for at least one second.
Although the stop lamp relay is on, the stop lamps remain off (do not come on) for at least one second.

PROBABLE CAUSES

Current trouble

Blown stop lamp bulbs
Malfunction of the stop lamp relay
The stop lamp switch improperly installed
Malfunction of the stop lamp switch
Damaged wiring harness or connector
Malfunction of the hydraulic unit assembly (integrated with ASC-ECU)

Past trouble

Carry out diagnosis with particular emphasis on the stop lamp switch, connector(s) or wiring harness between the stop lamp switch and ASC-ECU. For diagnosis procedures, refer to How to treat past trouble (GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).

DIAGNOSIS PROCEDURE

STEP 1. Check the stop lamp and the high-mounted stop lamp for proper function.

Check the stop lamp and the high-mounted stop lamp for proper operation when the brake pedal is depressed.

OK:
When the brake pedal is released: OFF
When the brake pedal is depressed: ON

Q. Is the check result normal?

	Go to Step 2.

	Diagnose the rear combination lamps (Refer to GROUP 54A - Rear Combination Lamp ). Then go to Step 9.

STEP 2. M.U.T.-III data list

Check the data list in the ETACS-ECU (Refer to GROUP 54A - ETACS-ECU

Item No.108: Stop lamp switch

Q. Is the check result normal?

	Go to Step 3.

	Diagnose the ETACS-ECU (Refer to GROUP 54A - ETACS-ECU ). Then go to Step 10.

STEP 3. M.U.T.-III actuator test

Execute the actuator test below to check the stop lamps for proper operation (Refer to

Item No.11: Stop lamp test mode

Q. Is the check result normal?

	Go to Step 8.

	Go to Step 4.

STEP 4. Measure the voltage at the ASC-ECU connector (ASTP terminal)

(1)Disconnect the connector, and measure at the wiring harness side.

(2)Check the voltage between the ASC-ECU connector ASTP terminal and body earth.
OK: System voltage

Q. Is the check result normal?

	Go to Step 6.

	Go to Step 5.

STEP 5. Check of short to earth, and open circuit in ASTP line between ASC-ECU connector and stop lamp relay connector. Check of short to earth, and open circuit in power supply line between fusible link and stop lamp relay connector.

(1)Disconnect the ASC-ECU connector and stop lamp relay connector, and measure at the wiring harness side.

(2)Measure the resistance in ASTP line between the ASC-ECU connector and the stop lamp relay connector.
OK: Continuity exists (2 Ω or less)

(3)Measure the resistance between the ASC-ECU connector ASTP terminal and body earth.
OK: No continuity (1 kΩ or more)

(4)Check the voltage in power supply line between the stop lamp relay connector and body earth.
OK: System voltage

Q. Is the check result normal?

	Go to Step 6.

	Repair the connector(s) or wiring harness. Then go to Step 10.

STEP 6. Check of open circuit in earth line between the stop lamp relay connector and body earth.

(1)Disconnect the stop lamp relay connector, and measure at the wiring harness side.

(2)Measure the resistance in earth line between the stop lamp relay connector and body earth.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?

	Go to Step 7.

	Repair the connector(s) or wiring harness. Then go to Step 10.

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

Execute the actuator test below to check the stop lamps for proper operation (Refer to

Item No.11: Stop lamp test mode

Q. Is the check result normal?

	Go to Step 8.

	Replace the stop lamp relay (Refer to GROUP 35A - On-vehicle Service ). Then go to Step 10.

STEP 8. Check of open circuit in STP line between the ASC-ECU connector and the stop lamp relay connector.

(1)Disconnect the ASC-ECU connector, and measure at the wiring harness side.

(2)Depress the brake pedal.

(3)Check the voltage between the ASC-ECU connector STP terminal and body earth.
OK: System voltage

Q. Is the check result normal?

	Go to Step 9.

	Repair the connector(s) or wiring harness. Then go to Step 10.

STEP 9. Check whether the diagnosis code is set again.

Check again if the diagnosis code is set.

(1)Erase the set diagnosis code.

(2)Ignition switch: "LOCK" (OFF)

(3)Ignition switch: "ON"

(4)Execute the actuator test (Refer to

Item No.11: Stop lamp test mode

Q. Is diagnosis code No. C1346 set?

	Replace the hydraulic unit assembly (integrated with ASC-ECU) (Refer to ). Then go to Step 10.

	The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 10. Check whether the diagnosis code is set again.

Check again if the diagnosis code is set.

(1)Erase the set diagnosis code.

(2)Ignition switch: "LOCK" (OFF)

(3)Ignition switch: "ON"

(4)Execute the actuator test (Refer to

Item No.11: Stop lamp test mode

Q. Is diagnosis code No. C1346 set?

	Return to Step 3.

	This diagnosis is complete.