Vehicles With Keyless Entry System
Seat Belt Warning Light: Seat Belt Warning Light does not Work Normally.Seat Belt Warning Light Circuit Part 1:
Seat Belt Warning Light Circuit Part 2:
NOTE: This troubleshooting procedure requires the use of scan tool MB991958 and SWS monitor kit MB991813. For details on how to use the SWS monitor, refer to "How to use SWS monitor." How To Use SWS Monitor
CIRCUIT OPERATION
- The ETACS-ECU operates the seat belt warning light according to the following switch signals and input signal:
- Ignition switch (IG1)
- Driver's seat belt switch
- Vehicle speed signal
- 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
- The driver's side seat belt switch may be defective
- The combination meter (seat belt warning light bulb or printed-circuit board) may be defective
- The ETACS-ECU may be defective
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
Required Special Tools:
- MB991223: Harness Set
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicles communication interface (V.C.I.)
- MB991827: MUT-III USB cable
- MB991911: MUT-III Main harness B
- MB991813: SWS monitor kit
- MB991806: SWS monitor cartridge
- MB991812: SWS monitor harness (for column-ECU)
- MB991922: Probe harness
STEP 1. Use scan tool MB991958 to select "ECU COMM CHK" on the SWS monitor display.
Check the ETACS-ECU.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958. Connect special tool MB991910 before connecting special tool MB991812. Be sure to connect special tool MB991806 after turning on special tool MB991824.
1. Connect the special tool. Refer to "How to connect SWS monitor." How to Connect SWS Monitor
2. When the ignition switch is turned to the "ON" position.
3. Operate scan tool MB991958 according to the procedure below to display "ECU COMM Check."
a. Select "Interactive Diagnosis."
b. Select "System Select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "ECU COMM Check."
4. Scan tool MB991958 should show "OK" on the "ECU COMM Check" menu for 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 not possible."
STEP 2. Check the input signal by using "DATA LIST" menu of the SWS monitor.
Tun the ignition switch to the "ON" position before checking input signals from the ignition switch (IG1).
1. Operate scan tool MB991958 according to the procedure below to display "ETACS ECU."
a. Select "Interactive Diagnosis."
b. Select "System Select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "Data List."
f. Select "ETACS ECU."
2. Check that normal conditions are displayed for the items described in the table.
Q: Does scan tool MB991958 display "IG SW (IG1)" as normal condition?
YES: Go to Step 3.
NO: Refer to Inspection Procedure O-2 "ETACS-ECU does not receive a signal from the ignition switch (IG1)."
STEP 3. Check the input signal (by using the Pulse check mode of the monitor).
Check input signal from the driver's side seat belt switch.
1. Operate scan tool MB991958 according to the procedure below to display "Pulse check."
a. Select "Interactive Diagnosis."
b. Select "System Select."
c. Select "SWS."
d. Select "Pulse Checking."
2. When the driver's seat belt is fastened, check if scan tool MB991958 sounds or not.
Q: Does scan tool MB991958 sound when the driver's side seat belt is fastened?
YES: Go to Step 4.
NO: Refer to Inspection Procedure P-3 "ETACS-ECU does not receive a signal from the driver's side seat belt switch."
STEP 4. Check the input signal (by using the Pulse check mode of the monitor).
Check the input signals from the vehicle speed sensor.
1. Operate scan tool MB991958 according to the procedure below to display "Pulse check."
a. Select "Interactive Diagnosis."
b. Select "System select."
c. Select "SWS."
d. Select "Pulse Checking."
2. When the vehicle speed exceeds 10 km/h (6.2 m.p.h.), check that scan tool MB991958 sounds or not.
Q: Does scan tool MB991958 sound when the vehicle speed exceeds 10 km/h (6.2 m.p.h.)?
YES: Go to Step 5.
NO: Refer to Inspection Procedure P-11 "ETACS-ECU does not receive a signal from the vehicle speed sensor."
STEP 5.Check ETACS-ECU connector C-118 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is ETACS-ECU connector C-118 in good condition?
YES: Go to Step 6.
NO: Repair or replace the damaged component(s). Refer to Harness Connector Inspection. Verify that the seat belt warning light illuminates normally.
STEP 6. Check at ETACS-ECU connector C-118 in order to check the ground circuit to the seat belt warning light.
1. Disconnect ETACS-ECU connector C-118, and measure at the wiring harness side.
2. Turn the ignition switch to the "ON" position.
3. Connect terminal 73 to ground.
Q: Does the seat belt warning light illuminate?
YES: Replace the ETACS-ECU. Verify that the seat belt warning light illuminates normally.
NO: Go to Step 7.
STEP 7. Check the seat belt warning light bulb.
Q: Is the seat belt warning light bulb in good condition?
YES: Go to Step 7.
NO: Replace the bulb. Verify that the seat belt warning light illuminates normally.
STEP 8. 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-41 terminal 52 and connector C-42 terminal 27. The measured resistance value should be roughly the same as the value measured in Step (2).
Q: Is the measured resistance 2 ohms or less?
YES: Go to Step 9.
NO (much the same): Repair or replace the combination meter (printed circuit board). Verify that the seat belt warning light illuminates normally.
STEP 9. Check combination meter connector C-41 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is combination meter connector C-41 in good condition?
YES: Go to Step 10.
NO: Repair or replace the damaged component(s). Refer to Harness Connector Inspection. Verify that the seat belt warning light illuminates normally.
STEP 10. Check the ignition switch (IG1) circuit to the combination meter. Measure the voltage at combination meter connector C-41.
1. Disconnect combination meter connector C-41 and measure the voltage available at the wiring harness side of the connector.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 52 and ground.
- The voltage should equal approximately 12 volts (battery positive voltage).
Q: Is the measured voltage approximately 12 volts (battery positive voltage)?
YES: Go to Step 12.
NO: Go to Step 11.
STEP 11. Check the wiring harness between combination meter connector C-41 (terminal 52) and the ignition switch (IG1).
NOTE: Also check junction block connectors C-108 and C-111 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If junction block connector C-108 or C-111 is damaged, repair or replace the damaged component(s) as described in Harness Connector Inspection.
Q: Is the wiring harness between combination meter connector C-41 (terminal 52) and the ignition switch (IG1) in good condition?
YES: No action is necessary and testing is complete.
NO: The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. Verify that the seat belt warning light illuminates normally.
STEP 12. Check the wiring harness between combination meter connector C-42 (terminal 27) and ETACS-ECU connector C-118 (terminal 73).
Q: Is the wiring harness between combination meter connector C-42 (terminal 27) and ETACS-ECU connector C-118 (terminal 73) in good condition?
YES: No action is necessary and testing is complete.
NO: The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. Verify that the seat belt warning light illuminates normally.