Inspection Procedure M-3

The ETACS-ECU does not Receive Any Signal from the Driver's Seat Belt Switch

Seat Belt Switch Input Circuit:

CIRCUIT OPERATION
The ETACS-ECU operates the following functions and equipment according to signal from the driver's seat belt switch:
- Seat belt tone alarm function
- Seat belt warning light

TECHNICAL DESCRIPTION (COMMENT)
If the signal is not normal, the equipment and functions, which are described in "CIRCUIT OPERATION", do not work normally,

TROUBLESHOOTING HINTS
- Malfunction of the driver's inner seat belt (driver's seat belt switch)
- Malfunction of the ETACS-ECU
- Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Test Harness Set
- MB991502: Scan Tool (MUT-II)







STEP 1. Check the driver's seat belt switch. Disconnect driver's seat belt switch connector D-20. Then check continuity between the switch terminals.

Q: Is the driver's seat belt switch in good condition?

YES: Go to Step 2.

NO: Replace the driver's seat belt. If the functions, which are described in "CIRCUIT OPERATION", work normally, the input signal from the driver's seat belt switch should be normal.




STEP 2. Measure at driver's seat belt switch connector D-20 in order to check the ground circuit to the driver's seat belt switch.

1. Disconnect driver's seat belt switch connector D-20, and measure at the harness side.
2. Measure the resistance value between terminal 2 and ground.
- The measured value should be 2 Ohm or less.

Q: Does the measured resistance value correspond with this range?

YES: Go to Step 5,

NO: Go to Step 3.




STEP 3. Check driver's seat belt switch connector D-20 for damage.

Q: Is the driver's seat belt switch connector D-20 in good condition?

YES: Go to Step 4.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. If the functions, which are described in "CIRCUIT OPERATION", work normally, the input signal from the driver's seat belt switch should be normal.







STEP 4. Check the wiring harness between driver's seat belt switch connector D-20 and ground.

NOTE: Also check joint connector C-06. If joint connector C-06 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between driver's seat belt switch connector D-20 and ground in good condition?

YES: No action to be taken.

NO: Repair the wiring harness. If the functions, which are described in "CIRCUIT OPERATION", work normally, the input signal from the driver's seat belt switch should be normal.







STEP 5. Check driver's seat belt switch connector D-20 and ETACS-ECU connector C-227 for damage.

Q: Are driver's seat belt switch connector D-20 and ETACS-ECU connector C-227 in good condition?

YES: Go to Step 6.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. If the functions, which are described in "CIRCUIT OPERATION", work normally, the input signal from the driver's seat belt switch should be normal.







STEP 6. Check the wiring harness between driver's seat belt switch connector D-20 and ETACS-ECU connector C-227.

Q: Is the wiring harness between driver's seat belt switch connector D-20 and ETACS-ECU connector C-227 in good condition

YES: Replace the ETACS-ECU. If the functions, which are described in "CIRCUIT OPERATION", work normally, the input signal from the driver's seat belt switch should be normal.

NO: Repair the wiring harness. If the functions, which are described in "CIRCUIT OPERATION", work normally, the input signal from the driver's seat belt switch should be normal.