H - Charts
Seat Belt Warning Light: Seat Belt Warning Light does not Work NormallySeat Belt Warning Light Circuit:
Connectors:
NOTE: This troubleshooting requires use of scan tool MB991502 and SWS monitor kit MB991862. For details of how to use the SWS monitor, refer to "How to use SWS monitor".
CIRCUIT OPERATION
- The ETACS-ECU operates the seat belt warning light according to the following switch signals:
- Ignition switch (IG1)
- Driver's seat belt switch
- If the driver turn the ignition switch to the "ON" position without fastening the seat belt, the seat belt warning light illuminates.
TECHNICAL DESCRIPTION (COMMENT)
If the seat belt warning light does not illuminate, the input circuit, the combination meter (seat belt warning light bulb or printed-circuit board) or the ETACS-ECU may be defective.
TROUBLESHOOTING HINTS
- Malfunction of driver's side seat belt switch
- Malfunction of combination meter (seat belt warning light bulb or printed-circuit board)
- Malfunction of the ETACS-ECU
DIAGNOSIS
Required Special Tools:
- MB991223: Test Harness Set
- MB991502: Scan Tool (MUT-II)
- MB991862: SWS monitor kit
STEP 1. Use scan tool to select "ECU CHECK" on the SWS monitor display.
Check the ETACS-ECU.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502. Also connect SWS monitor kit MB991862 after turning on scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Connect SWS monitor kit MB991862 to the column switch connector.
3. When the ignition switch is turned to the "LOCK" (OFF) position, scan tool MB991502 should show "OK" on the "ETACS ECU" menu.
Q: Is "OK" displayed on the "ETACS ECU" menu?
YES: Go to STEP 2.
NO: Refer to Inspection Procedure A-3 "Communication with ETACS-ECU is impossible."
STEP 2. Check the input signal by using service data of the SWS monitor.
Turn the ignition switch to the "ON" position before checking input signals from the ignition switch (IG1).
Select "ETACS ECU" (DATALIST), and check that normal conditions are displayed on the items described in the table.
Q: Is normal condition displayed "IG SW (IG1)"?
YES: Go to STEP 3.
NO: Refer to Inspection Procedure L-2 "ETACS-ECU does not receive a signal from the ignition switch (IG1)."
STEP 3. Check the input signal (by using the Pulse check).
Check input signal from the driver's side seat belt switch.
- When the driver's seat belt is fastened, check if scan tool MB991502 sounds or not.
Q: Does scan tool MB991502 sound when the driver's side seat belt is fastened?
YES: Go to Step 4.
NO: Refer to Inspection Procedure M-3 "ETACS-ECU does not receive a signal from the driver's side seat belt switch."
STEP 4. Check at ETACS-ECU connector C-228 in order to check the ground circuit to the seat belt warning light.
1. Disconnect ETACS-ECU connector C-228, and measure at the wiring harness side.
2. Turn the ignition switch to the "ON" position.
3. Connect terminal No. 73 to ground.
Q: Does the seat belt warning light illuminate?
YES: Replace the ETACS-ECU. Check that the seat belt warning light illuminates normally.
NO: Go to Step 5.
STEP 5. Check the seat belt warning light bulb.
Q: Is the seat belt warning light bulb in good condition?
YES: Go to Step 6.
NO: Replace the bulb. Check that the seat belt warning light illuminates normally.
STEP 6. Check the combination meter (printed-circuit board).
1. Remove the combination meter.
2. Remove the seat belt warning light bulb. Then measure the resistance value between the bulb terminals.
3. Install the bulb to the combination meter, and then measure the resistance value between connector C-01 terminal 9 and connector C-02 terminal 35. The measured resistance value should be roughly the same as the value measured in Step 2.
Q: Are these two resistance values extremely different?
YES: Repair or replace the combination meter (printed circuit board). Check that the seat belt warning light illuminates normally.
NO (much the same): Go to Step 7.
STEP 7. Measure at combination meter connector C-01 in order to check the ignition switch (IG1) line of the power supply to the combination meter.
1. Disconnect combination meter connector C-01, and measure at the wiring harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 9 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).
Q: Does the measured voltage correspond with this range?
YES: Go to Step 10.
NO: Go to Step 8.
STEP 8. Check combination meter connector C-01 for damage.
Q: Is combination meter connector C-01 in good condition?
YES: Go to Step 9.
NO: Repair or replace the connector. Refer to Harness Connector Inspection. Check that the seat belt warning light illuminates normally.
STEP 9. Check the wiring harness between combination meter connector C-01 and the ignition switch (IG1).
NOTE: Also check junction block connectors C-211, C-214 and joint connector C-21. If junction block connector C-211, C-214 or joint connectors C-21 is damaged, repair or replace the connector as described in Harness Connector Inspection.
Q: Is the wiring harness between combination meter connector C-01 and the ignition switch (IG1) in good condition?
YES: No action to be taken.
NO: Repair the wiring harness. Check that the seat belt warning light illuminates normally.
STEP 10. Check combination meter connector C-02 and ETACS-ECU connector C-228 for damage.
Q: Are combination meter connector C-02 and ETACS-ECU connector C-228 in good condition?
YES: Go to Step 11.
NO: Repair or replace the connector. Refer to Harness Connector Inspection. Check that the seat belt warning light illuminates normally.
STEP 11. Check the wiring harness between combination meter connector C-02 and ETACS-ECU connector C-228.
Q: Is the wiring harness between combination meter connector C-02 and ETACS-ECU connector C-228 in good condition?
YES: No action to be taken.
NO: Repair the wiring harness. Check that the seat belt warning light illuminates normally.