ASC
DTC C1000: Abnormality in stop light switch circuit
CAUTION:
^ If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be set. Prior to this diagnosis, diagnose the CAN bus lines.
^ Whenever ECU is replaced, ensure that the CAN bus lines are normal.
^ When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor, the G and yaw rate sensor and brake fluid pressure sensor.
OPERATION
ETACS-ECU sends the ON signal generated when the brake pedal is depressed and OFF signal generated when it is released to ASC-ECU via the CAN bus lines.
DTC SET CONDITIONS
This diagnostic trouble code is set in the following case.
^ When the vehicle has run for a long time with the stop light switch turned ON.
^ When there is difference between the stop light state and the vehicle's behavior
PROBABLE CAUSES
^ Improper adjustment of stop lamp switch installation position
^ Malfunction of the stop lamp switch
^ Malfunction of the stop lamp
^ Damaged wiring harness and connectors
^ ETACS-ECU malfunction
^ ASC-ECU malfunction
DIAGNOSIS
Required Special Tools:
^ MB991958 Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface (V.C.I.)
^ MB991827 M.U.T.-III USB Cable
^ MB991910 M.U.T.-III Main Harness
STEP 1. M.U.T.-III CAN bus diagnostics
Use scan tool to diagnose the CAN bus lines.
Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the CAN bus lines. On completion, go to Step 2.
STEP 2. Diagnostic trouble code recheck after resetting CAN bus lines
Q: Is DTC C1000 set?
YES: Go to Step 3.
NO: The procedure is complete.
STEP 3. Check the battery.
Refer to Battery Test.
Q: Is the battery in good condition?
YES: Go to Step 4.
NO: Charge or replace the battery. Then go to Step 19.
STEP 4. Stop light operation check
1) Turn the ignition switch to the ON position.
2) Check the stop light operation when the brake pedal is depressed. Check that the stop light 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?
YES: Go to Step 20.
NO: Go to Step 5.
STEP 5. Check for stop lamp switch installation
Q: Is the check result normal?
YES: Go to Step 6.
NO: Install the stop light switch correctly. Then, go to Step 23.
STEP 6. Connector check: C-124 stop lamp switch connector
Q: Is the check result normal?
YES: Go to Step 7.
NO: Repair the defective connector.
STEP 7. Stop lamp switch continuity check
1) Remove the stop light switch.
2) Connect the circuit tester (range) to the stop light 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 light switch is in good condition.
Q: Is the check result normal?
YES: Go to Step 8.
NO: Replace the stop light switch. Then go to Step 23.
STEP 8. M.U.T.-III other system diagnostic trouble code
Check that no DTC is set by the rear combination light.
Q: Is the check result normal?
YES: Go to Step 9.
NO: Carry out the diagnosis of rear combination light. Then go to Step 22.
STEP 9. ETACS-ECU fuse No.2 check
Q: Is the check result normal?
YES: Go to Step 14.
NO: Go to Step 10.
STEP 10. Connector check: C-129 joint connector, C-304 ETACS-ECU connector, C-312 ETACS-ECU connector
Q: Is the check result normal?
YES: Go to Step 11.
NO: Repair the defective connector.
STEP 11. Resistance measurement at C-312 ETACS-ECU connector
1) Removal the C-124 stop lamp switch connector, C-129 joint connector and C-312 ETACS-ECU connector.
2) Measure the C-312 ETACS-ECU connector at the wiring harness side.
3) Resistance between the terminal No.16 and the body ground.
OK: No continuity
Q: Is the check result normal?
YES: Go to Step 12.
NO: Repair the harness between the C-129 joint connector terminal No.9 and C-312 ETACS-ECU connector terminal No.16. Then replace the fuse No.2.
STEP 12. Resistance measurement at C-304 ETACS-ECU connector
1) Removal the C-124 stop lamp switch connector and C-304 ETACS-ECU connector.
2) Measure the C-304 ETACS-ECU connector at the wiring harness side.
3) Resistance between the terminal No.1 and the body ground.
OK: No continuity
Q: Is the check result normal?
YES: Go to Step 13.
NO: Repair the harness between the C-124 stop lamp switch connector terminal No.2 and C-304 ETACS-ECU connector terminal No.1. Then replace the fuse No.2.
STEP 13. Resistance measurement at C-124 stop light switch connector
1) Removal the C-124 stop light switch connector and C-129 joint connector.
2) Measure the C-124 stop light connector at the wiring harness side.
3) Resistance between the terminal No.1 and the body ground.
OK: No continuity
Q: Is the check result normal?
YES: Replace the fuse No.2.
NO: Repair the harness between the C-124 stop lamp switch connector terminal No.1 and C-129 joint connector terminal No.9, and between the C-124 stop lamp switch connector terminal No.1 and C-312 ETACS-ECU connector terminal No.16. Then replace the fuse No.2.
STEP 14. Connector check: C-304 ETACS-ECU connector
Q: Is the check result normal?
YES: Go to Step 15.
NO: Repair the defective connector.
STEP 15. Measure the voltage at the C-304 ETACS-ECU connector.
CAUTION: The measurement must be performed without the brake pedal depressed (not operated). Measure the voltage between the terminal No. 1 and the body ground by backprobing.
OK: Approximately battery voltage
Q: Is the check result normal?
YES: Go to Step 16.
NO: Replace the ETACS-ECU. Then go to Step 23.
STEP 16. Connector check: C-124 stop light switch connector
Q: Is the check result normal?
YES: Go to Step 17.
NO: Repair the defective connector.
STEP 17. Voltage measurement at the C-124 stop light switch connector
1) Disconnect the connector, and measure at the wiring harness side.
2) Measure the voltage between the terminal No. 2 and the body ground.
OK: Approximately battery voltage
Q: Is the check result normal?
YES: Go to Step 18.
NO: An open circuit may be present in the wiring harness between C-304 ETACS-ECU connector terminal No. 1 and C-124 stop light switch connector terminal No.2. Repair the wiring harness.
STEP 18. Connector check: C-129 joint connector
Q: Is the check result normal?
YES: Go to Step 19.
NO: Repair the defective connector.
STEP 19. Voltage measurement at the C-129 joint connector
CAUTION: The measurement must be performed with the brake pedal depressed.
1) Disconnect the connector, and measure at the wiring harness side.
2) Measure the voltage between the terminal No. 9 and the body ground.
OK: Approximately battery voltage
Q: Is the check result normal?
YES: Go to Step 20.
NO: An open circuit may be present in the wiring harness between C-129 joint connector terminal No. 9 and C-124 stop light switch connector terminal No.1. Repair the wiring harness.
STEP 20. Connector check: C-312 ETACS-ECU connector
Q: Is the check result normal?
YES: Go to Step 21.
NO: Repair the defective connector.
STEP 21. Measure the voltage at the C-312 ETACS-ECU connector.
1) Without disconnecting the connector, measure by backprobing.
2) Measure the voltage between the terminal No. 16 and the body ground.
OK:
The brake pedal is released: Approximately 0 V
The brake pedal is depressed: Approximately battery voltage
Q: Is the check result normal?
YES: Go to Step 22.
NO: An open circuit may be present in the wiring harness between C-312 ETACS-ECU connector terminal No. 16 and C-124 stop light switch connector terminal No. 1. Repair the wiring harness.
STEP 22. Check whether the diagnostic trouble code is reset.
Q: Is DTC 1000 set?
YES: Replace the ASC-ECU. Then go to Step 23.
NO: The trouble can be an intermittent malfunction.
STEP 23. Check whether the diagnostic trouble code is reset.
Q: Is DTC 1000 set?
YES: Return to Step 1.
NO: The procedure is complete.