I - Charts
Seat Belt Warning Light Circuit:
Connectors:
CIRCUIT OPERATION
The seat belt warning light illuminates when the driver turns the ignition switch to "ON" position without wearing the seat belt.
TECHNICAL DESCRIPTION (COMMENT)
The ETACS-ECU illuminates the seat belt warning light according to the input signals from the following switches:
- Ignition switch (IG1)
- Driver's seat belt switch
If the seat belt warning light does not illuminate, the relevant input signal circuit, the combination meter (seat belt warning light bulb or printed-circuit board) or the ETACS-ECU may be defective.
TROUBLESHOOTING HINTS
- Malfunction of the driver's side seat belt switch
- Malfunction of the combination meter (seat belt warning light bulb or printed-circuit board)
- Malfunction of the ETACS-ECU
- Damaged harness wires or connectors
DIAGNOSIS
Required Special Tools:
MB991223: Test Harness Set
MB991502: Scan Tool (MUT-II)
MB991529: Diagnostic Trouble Code Check Harness
STEP 1. Check the input signal.
Check the input signals from the following switches:
- Ignition switch (IG1)
- Driver's side seat belt switch
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Check that the tone alarm of scan tool MB991502 sounds when the input signal enters.
1. Use special tool MB991529 to connect a voltmeter between ground terminal 4 or 5 and ETACS-ECU terminal 9 of the data link connector.
2. Check that the voltmeter indicator deflects once when the input signal.
If one of the input signal checks shows a defect, check the relevant input signal circuit.
If none of the input signal checks shows a defect, go to Step 2.
STEP 2. Check the seat belt warning light circuit at the ETACS-ECU connector C-111.
1. Disconnect the ETACS-ECU connector C-111 and measure at the harness side.
2. Turn the ignition switch to "ON" position.
3. Connect terminal 54 to the ground.
- The seat belt warning light should illuminate.
If the seat belt warning light does not illuminate, go to Step 3.
If the seat belt warning light illuminate, replace the ETACS-ECU.
The seat belt warning light should work normally.
STEP 3. Check the seat belt warning light bulb.
If the seat belt warning light bulb has blown, replace it. The seat belt warning light should work normally.
If the seat belt warning light bulb is in good condition, go to Step 4.
STEP 4. Check the combination meter (printed-circuit board).
1. Remove the combination meter.
2. Remove the seat belt warning light bulb. Then measure the resistance between the bulb terminals.
3. Install the bulb to the combination meter, and then measure the resistance between connector C-41 terminal 52 and connector C-42 terminal 26. The resistance reading at this time should be much the same as the resistance measured at Step (2).
If the two resistance values are extremely different each other, repair or replace the combination meter (printed circuit board).
The seat belt warning light should work normally.
If the two resistance values are much the same, go to Step 5.
STEP 5. Check the combination meter connector C-42 and ETACS-ECU connector C-111 for damage.
If the combination meter connector C-42 and ETACS-ECU connector C-111 are damaged, repair or replace them. Refer to Harness Connector Inspection.
The seat belt warning light should work normally.
If the connectors are in good condition, go to Step 6.
STEP 6. Check the harness wire between combination meter connector C-42 and ETACS-ECU connector C-111.
If the harness wire between combination meter connector C-42 and ETACS-ECU connector C-111 is damaged, repair it.
The seat belt warning light should work normally.
If the harness wire is in good condition, go to Step 7.
STEP 7. Check the combination meter connector C-41 for damage.
If the combination meter connector C-41 is damaged, repair or replace it. Refer to Harness Connector Inspection.
The seat belt warning light should work normally. If the connector is in good condition, go to Step 8.
STEP 8. Check the harness wires between combination meter connector C-41 and ignition switch (IG1).
NOTE: After checking intermediate connectors C-101 and C-104, check the wires. If intermediate connectors C-101 and C-104 are damaged, repair or replace them. Refer to Harness Connector Inspection.
If the harness wires between combination meter connector C-41 and ignition switch (IG1) are damaged, repair or replace them.
The seat belt warning light should work normally.