Inspection Procedure 2

When the Seat Belt is not Fastened and the Ignition Switch is Turned to the "ON" Position, the Seat Belt Warning Light Illuminates or Flashed, but the Seat Belt Tone Alarm does not Sound.

Seat Belt Switch Circuit:

CIRCUIT OPERATION
- The system determines whether the seat belt is fastened by the seat belt switch.
- The system flashes the seat belt warning light for 6 seconds after the ignition switch is turned "ON," and also sounds the seat belt tone alarm if the seat belt is not fastened.

TECHNICAL DESCRIPTION (COMMENT)
There may be a malfunction in the seat belt buckle switch circuit.

TROUBLESHOOTING HINTS
- Malfunction of the seat belt buckle switch
- Malfunction of the ETACS-ECU
- Damaged wiring harnesses or connectors

DIAGNOSIS

Required Special Tools:
- MB991502: Scan tool (MUT-II)
- MB991529: Diagnostic Trouble Code Check Harness

STEP 1. Check the input signal using either scan tool MB991502 or a voltmeter.

CAUTION: The scan tool MB991502 should be connected or disconnected after turning the ignition switch to the "OFF" position.




When using scan tool MB991502.
1. Connect the scan tool MB991502 to the data link connector.
2. If tone alarm of scan tool MB991502 sounds once when the seat belt buckle switch is operated (ON/OFF), the ETACS-ECU input signal for that switch circuit system is normal.




When using a voltmeter
1. Use special tool MB991529 to connect a voltmeter between the ground terminal 4 or 5 and the ETACS terminal 9 of the data link connector.
2. If the voltmeter indicator deflects once when the seat belt buckle switch is operated (ON/OFF), the ETACS-ECU input signal for that switch circuit system is normal.

Q: Is the switch circuit system normal?
YES: Replace the ETACS-ECU. Then go to Step 5.
NO: Go to Step 2.




STEP 2. Check the seat belt buckle switch continuity.

Q: No continuity should exist when the seat belt is fastened, while continuity should exist when the seat belt is unfastened?
YES: Go to Step 3.
NO: Replace the seat belt buckle. Then go to Step 5.







STEP 3. Check the harness wires between ETACS-ECU connector D-11 and seat belt buckle switch connector E-35.

NOTE: Check the intermediate connector D-13 and E-42 and then the wiring harness. If the intermediate connectors D-13 and E-42 are damaged, repair or replace them. Refer to Harness Connector Inspection. Then go to Step 5.

Q: Is the harness wires between ETACS-ECU connector D- 11 and seat belt buckle switch connector in good condition?
YES: Go to Step 4.
NO: Repair them. Then go to Step 5.




STEP 4. Check the harness wire between seat belt buckle switch connector E-35 and ground.

Q: Is the harness wire between seat belt buckle switch connector E-35 and ground in good condition?
YES: Go to Step 5.
NO: Repair them. Then go to Step 5.

STEP 5. Check symptoms.

Q: The seat belt warning light illuminate or flash, but does the seat belt tone alarm sound?
YES: This diagnosis is complete. (If no malfunctions are not found in all steps, an intermittent malfunction is suspected. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.)
NO: There is no action to be taken.