Inspection Procedure O-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 described in "CIRCUIT OPERATION", do not work normally.

TROUBLESHOOTING HINTS
- The driver's inner seat belt (driver's seat belt switch) may be defective.
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector.
- The ETACS-ECU may be defective.

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe




STEP 1. Check driver's seat belt switch connector D-20 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

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

YES: Go to Step 2.

NO: Repair or replace the damaged component(s). 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 2. 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 3.

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

STEP 3. Check the battery ground circuit to the driver's seat belt switch. Measure the resistance at driver's seat belt switch connector D-20.




1. Disconnect driver's seat belt switch connector D-20 and measure the resistance available at the wiring harness side of the connector.




2. Measure the resistance value between terminal 2 and ground.
- The resistance should equal 2 ohms or less.

Q: Is the measured resistance 2 ohms or less?

YES: Go to Step 5.

NO: Go to Step 4.







STEP 4. Check the wiring harness between driver's seat belt switch connector D-20 (terminal 2) and ground.

NOTE: Also check joint connector C-06 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-06 is damaged, repair or replace the damaged component(s) as described in Harness Connector Inspection.

Q: Is the wiring harness between driver's seat belt switch connector D-20 (terminal 2) and ground 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. 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 ETACS-ECU connector C-227 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is ETACS-ECU connector C-227 in good condition?

YES: Go to Step 6.

NO: Repair or replace the damaged component(s). 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 (terminal 1) and ETACS-ECU connector C-227 (terminal 21).

Q: Is the wiring harness between driver's seat belt switch connector D-20 (terminal 1) and ETACS-ECU connector C-227 (terminal 21) in good condition?

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

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. If the functions described in "CIRCUIT OPERATION", work normally, the input signal from the driver's seat belt switch should be normal.