Code No.C1340: Stop lamp switch circuit malfunction










caution If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Diagnose the CAN bus lines before the diagnosis codes (Refer to GROUP 54C, CAN bus-line diagnostic flow ).

OPERATION

  • ASTC-ECU monitors whether the stop lamp switch is "ON" or "OFF."

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set in the following case.

  • When the vehicle has been driving at a vehicle speed of 15 km/h or more for 15 minutes or longer with the stop lamp switch turned ON.
  • With the stop lamp switch OFF, the decelerated speed G is occurred at the specified value or more.

PROBABLE CAUSES
The most likely causes for these diagnosis codes to set are:

  • Malfunction of the stop lamp switch
  • Damaged wiring harness or connector
  • Malfunction of the hydraulic unit assembly (integrated with ASTC-ECU)

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 3.
Repair the CAN bus lines. (Refer to GROUP 54C - Troubleshooting .) On completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting CAN bus lines

Q. Is the diagnosis code No.C1340 set?
Go to Step 3.
This diagnosis is complete.

STEP 3. Stop lamp and high-mount stop lamp operation check
Check the stop lamp and high-mount stop lamp operation when the brake pedal is depressed. Check that the stop lamp and high-mount stop lamp illuminates when the brake pedal is depressed and that it goes out when the brake pedal is released.
OK:
    When the brake pedal is released: OFF
    When the brake pedal is depressed: ON

Q. Is the check result normal?
Go to Step 11.
Go to Step 4.

STEP 4. Connector check: C-139 stop lamp switch connector

Q. Is the check result normal?
Go to Step 5.
Repair or replace it, and go to Step 13.

STEP 5. Check for stop lamp switch installation
Refer to GROUP 35A - On-vehicle Service .

Q. Is the check result normal?
Go to Step 6.
Install the stop lamp switch correctly (Refer to GROUP 35A - On-vehicle Service .) Then go to Step 13.

STEP 6. Stop lamp switch continuity check
(1)Remove the stop lamp switch (Refer to GROUP 35A - Brake Pedal .)

(2)Connect the circuit tester (Ω range) to the stop lamp switch connector terminals No.1 and No.2.
(3)When no continuity is detected with the plunger pressed from the edge of the outer case by the dimension shown in the figure and when continuity is detected with the plunger released, the stop lamp switch is in good condition.

Q. Is the check result normal?

Go to Step 7.

Replace the stop lamp switch (Refer to GROUP 35A - Brake Pedal .) Then go to Step 13.

STEP 7. Connector check: A-68 ASTC-ECU connector, C-02 joint connector, F-02 rear combination lamp (stop: LH) connector, F-10 rear combination lamp (stop: RH) connector, F-06 high mounted stop lamp connector, C-15 intermediate connector, C-18 intermediate connector

Q. Is the check result normal?
Go to Step 8.
Repair or replace it, and go to Step 13.

STEP 8. Voltage measurement at C-139 stop lamp switch connector.
(1)Remove C-139 stop lamp switch connector, and measure at the wiring harness connector side.
(2)Measure the voltage between terminal No.2 and body earth.
OK: System voltage

Q. Is the check result normal?
Go to Step 9.
An open or short to power supply has occurred in the wiring harness between fusible link No.23 and C-139 stop lamp switch connector terminal No.2 and Fuse No.12, therefore, repair it. Then go to Step 13.

STEP 9. Resistance measurement at C-139 stop lamp switch connector.
(1)Disconnect the A-68 ASTC-ECU connector, C-139 stop lamp switch connector, F-02 rear combination lamp (stop: LH) connector, F-10 rear combination lamp (stop: RH) connector, F-06 high mounted stop lamp connector, and measure the resistance at C-139 stop lamp switch connector harness side.
(2)Measure the resistance between terminal No.1 and body earth.
OK: No continuity

Q. Is the check result normal?
Go to Step 10.
A short to power supply has occurred in the wiring harness between C-139 stop lamp switch connector terminal No.1 and F-02 rear combination lamp (stop: LH) connector terminal No.1, or between C-139 stop lamp switch connector terminal No.1 and F-06 high mounted stop lamp connector terminal No.2, or between C-139 stop lamp switch connector terminal No.1 and F-10 rear combination lamp (stop: RH) connector terminal No.1, therefore, repair it.Then go to Step 13.

STEP 10. Resistance measurement at C-139 stop lamp switch connector and C-02 joint connector.
(1)Disconnect the C-139 stop lamp switch connector and C-02 joint connector, and measure at the harness side.
(2)Measure the resistance between C-139 stop lamp switch connector terminal No.1 and C-02 joint connector terminal No.7.
OK: Continuity exists (2 Ω or less)

Q. Is the check result normal?
Go to Step 12.
Repair the wiring harness, and then go to Step 13.

STEP 11. Voltage measurement at A-68 ASTC-ECU connector.

(1)Disconnect the A-68 ASTC-ECU connector, and connect special tool ASC check harness (MB992159) to the wiring harness-side connector.
note Do not connect special tool ASC check harness (MB992159) to the ASTC-ECU.
(2)Turn the ignition switch to the "ON" position.
(3)Measure the voltage between terminal No.7 and body earth.
OK:
  • When the brake pedal is released: 1 V or less
  • When the brake pedal is depressed: System voltage

Q. Is the check result normal?

Go to Step 12.

An open circuit in signal line has occurred in the wiring harness between A-68 ASTC-ECU connector terminal No.7 and C-02 joint connector terminal No.1, therefore, repair it. Then go to Step 13.

STEP 12. Diagnosis code recheck

Q. Is the diagnosis code No.C1340 set?
Replace the ASTC-ECU (Refer to ). Then go to Step 13.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)

STEP 13. Diagnosis code recheck

Q. Is the diagnosis code No.C1340 set?
Return to Step 1.
This diagnosis is complete.