Inspection Procedure B-3

Tone Alarm: Seat Belt Tone Alarm Function does not Work Normally

Seat Belt Tone Alarm Function:

NOTE: This troubleshooting requires use of scan tool MB991502 and SWS monitor kit MB991862. For details of how to use the SWS monitor, refer to "How to use SWS monitor".

CIRCUIT OPERATION
The ETACS-ECU operates the seat belt tone alarm function intermittently according to signals from the following switches:
- Ignition switch (IG1): ON
- Driver's seat belt switch: ON

The ETACS-ECU operates the seat belt tone alarm function intermittently under the following conditions:
- ignition switch: ON or START
- Driver's seat belt: UNFASTENED

TECHNICAL DESCRIPTION (COMMENT)
If the function does not work normally, the input circuit system from the switches or the ETACS-ECU may be defective (refer to "CIRCUIT OPERATION"),

TROUBLESHOOTING HINTS
- Malfunction of 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)
- MB991862: SWS monitor kit







STEP 1. Use scan tool to select "ECU CHECK" on the SWS monitor display.

Check the ETACS-ECU.

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. Also connect SWS monitor kit MB991862 after turning on scan tool MB991502.

1. Connect scan tool MB991502 to the data link connector.
2. Connect SWS monitor kit MB991862 to the column switch connector.
3. When the ignition switch is turned to the "LOCK" (OFF) position, scan tool MB991502 should show "OK" on the "ETACS ECU" menu.

Q: Is "OK" displayed on the "ETACS ECU" menu?

YES: Go to STEP 2.

NO: Refer to Inspection Procedure A-3 "Communication with ETACS-ECU is impossible."







STEP 2. Check the input signal by using service data of the SWS monitor.

Turn the ignition switch to the "ON" position before checking input signals from the ignition switch (IG1).




Select "ETACS ECU" (DATALIST), and check that normal conditions are displayed on the items described in the table.

Q: Is normal condition displayed on the "IG SW (IG1)"?

YES: Go to STEP 3.

NO: Refer to Inspection Procedure L-2 "ETACS-ECU does not receive a signal from the ignition switch (IG1)."




STEP 3. Check the input signal (by using the Pulse check).
Check input signal from the driver's side seat belt switch.
- When the driver's seat belt is unfastened, check if scan tool MB991502 sounds or not.

Q: Does scan tool MB991502 sound when the driver's side seat belt is unfastened?

YES: Replace the ETACS-ECU. Check that the seat belt tone alarm function works normally.

NO: Refer to Inspection Procedure M-3 "ETACS-ECU does not receive a signal from the driver's side seat belt switch."