INSPECTION PROCEDURE H-1: Seat belt warning light: Seat belt warning light does not work normally.: Diagnosis
Required Special Tools:
- MB991223: Test Harness Set
- MB991502: Scan Tool (MUT-II)
- MB991529: Diagnostic Trouble Code Check Harness
- STEP 1. Verify the method of the input signal
Q: Which is to be used, the scan tool or the voltmeter to check the input signal?
Scan tool MB991502 : Go to Step 2.
Voltmeter : Go to Step 3.
- STEP 2. Check the input signal (by using scan tool MB991502).
Check the input signals from the following switches:
- Ignition switch (IG1)
- Driver's side seat belt switch
- Speed sensor
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.- Connect scan tool MB991502 to the data link connector.
- Check that the tone alarm of scan tool MB991502 sounds when the input signal enters.
Q: Does the tone alarm of scan tool MB991502 sound when the input signal enters?
YES : Go to Step 4.
NO:
- Scan tool MB991502 does not sound when the ignition switch is turned from "ACC" to "ON": Refer to INSPECTION PROCEDURE O-2 "THE IGNITION SWITCH (IG1) SIGNAL IS NOT SENT TO THE ETACS-ECU ."
- Scan tool MB991502 does not sound when the driver's seat belt is unfastened: Refer to INSPECTION PROCEDURE O-7 "THE DRIVER'S SEAT BELT SWITCH SIGNAL IS NOT SENT TO THE ETACS-ECU ."
- Scan tool MB991502 does not sound when the vehicle speed has reached from 24 km/h or lower to 25 km/h or higher: Refer to INSPECTION PROCEDURE O-13 "THE SPEED SENSOR SIGNAL IS NOT SENT TO THE ETACS-ECU ."
- STEP 3. Check the input signal (by using a voltmeter).
Check the input signals from the following switches:
- Ignition switch (IG1)
- Driver's side seat belt switch
- Speed sensor
- Use special tool MB991529 to connect a voltmeter between ground terminal 4 or 5 and ETACS-ECU terminal 9 of the data link connector.
- Check that the voltmeter indicator deflects once when the input signal enters.
Q: Does the voltmeter indicator deflect?
YES : Go to Step 4.
NO:
- The voltmeter needle does not fluctuate when the ignition switch is turned from "ACC" to "ON": Refer to INSPECTION PROCEDURE O-2 "THE IGNITION SWITCH (IG1) SIGNAL IS NOT SENT TO THE ETACS-ECU ."
- The voltmeter needle does not fluctuate when the driver's seat belt is unfastened: Refer to INSPECTION PROCEDURE O-7 "THE DRIVER'S SEAT BELT SWITCH SIGNAL IS NOT SENT TO THE ETACS-ECU ."
- Scan tool MB991502 does not sound when the vehicle speed has reached from 24 km/h or lower to 25 km/h or higher: Refer to INSPECTION PROCEDURE O-13 "THE SPEED SENSOR SIGNAL IS NOT SENT TO THE ETACS-ECU ."
- STEP 4. Check the seat belt warning light circuit at the ETACS-ECU connector C-318.
- Disconnect the ETACS-ECU connector C-318 and measure at the wiring harness side.
- Turn the ignition switch to the "ON" position.
- Connect terminal 73 to the ground.
Q: Does the seat belt warning light illuminate?
YES : Replace the ETACS-ECU. The seat belt warning light should work normally.
NO: Go to Step 5.
- STEP 5. Check the ignition switch (IG1) circuit to the combination meter. Test at combination meter connector C-101.
- Disconnect the combination meter connector C-101 and measure the voltage available at the wiring harness side of the connector.
- Turn the ignition switch to the "ON" position.
- Measure the voltage between terminal 12 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 8.
NO: Go to Step 6.
- STEP 6. Check the combination meter connector C-101 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is combination meter connector C-101 in good condition?
YES : Go to Step 7.
NO: Repair or replace the damaged component(s). Refer to , HARNESS CONNECTOR INSPECTION . The seat belt warning light should work normally.
- STEP 7. Check the wiring harness between combination meter connector C-101 (terminal 12) and ignition switch (IG1).
NOTE: Also check junction block connectors C-308 and C-311 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If junction block connectors C-308 or C-311 are damaged, repair or replace the damaged component(s) as described in , HARNESS CONNECTOR INSPECTION .
Q: Are the wiring harness between combination meter connector C-101 (terminal 12) and ignition switch (IG1) in good condition?
YES : No action is necessary and testing is complete.
NO: Repair or replace the them. The seat belt warning light should work normally.
- STEP 8. Check the combination meter connector C-101 and ETACS-ECU connector C-318 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are combination meter connector C-101 and ETACS-ECU connector C-318 in good condition?
YES : Go to Step 9.
NO: Repair or replace the damaged component(s). Refer to , HARNESS CONNECTOR INSPECTION . The seat belt warning light should work normally.
- STEP 9. Check the wiring harness between combination meter connector C-101 (terminal 7) and ETACS-ECU connector C-318 (terminal 73).
Q: Is the wiring harness between combination meter connector C-101 (terminal 7) and ETACS-ECU connector C-318 (terminal 73) in good condition?
YES : Replace the combination meter. The seat belt warning light should work normally.
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. The seat belt warning light should work normally.