Inspection Procedure B-5

INSPECTION PROCEDURE B-5: Tone alarm: Seat belt tone alarm function does not work normally.

TECHNICAL DESCRIPTION (COMMENT)
The ETACS-ECU operates the seat belt tone alarm function, based on input signals from the following switches:
- Ignition switch (IG1)
- Driver's seat belt switch
If the function does not work normally, a defect on the relevant circuit or the ETACS-ECU may be suspected.

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

DIAGNOSIS
Required Special Tools:
- MB991223: Test Harness Set
- MB991502: Scan Tool (MUT-II)
- MB991529: Diagnostic Trouble Code Check Harness

STEP 1. Verify the method of the input signal

Q: Which is to be used, the scan tool or the voltmeter to check the input signal?
Scan tool MB991502 : Go to Step 2.
Voltmeter : Go to Step 3.

STEP 2. Check the input signal (by using scan tool MB991502).
Check the input signals from the following switches:
- Ignition switch (IG1)
- Driver's seat belt switch

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.




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.

Q: Does the tone alarm of scan tool MB991502 sound when the input signal enters.

YES : Replace the ETACS-ECU. The seat belt tone alarm function should work normally.

NO :
- Scan tool MB991502 does not sound when the ignition switch is turned from "ACC" to "ON": Refer to Inspection Procedure O-2 "The ignition switch (IG1) signal is not sent to the ETACS-ECU." Inspection Procedure O-2
- Scan tool MB991502 does not sound when the driver's seat belt is unfastened: Refer to Inspection Procedure O-7 "The driver's seat belt switch signal is not sent to the ETACS-ECU." Inspection Procedure O-7

STEP 3. Check the input signal (by using a voltmeter).
Check the input signals from the following switches:
- Ignition switch (IG1)
- Driver's seat belt switch




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 enters.

Q: Does the voltmeter indicator deflect?

YES : Replace the ETACS-ECU. The seat belt tone alarm function should work normally.

NO :
- The voltmeter needle does not fluctuate when the ignition switch is turned from "ACC" to "ON": Refer to Inspection Procedure O-2 "The ignition switch (IG1) signal is not sent to the ETACS-ECU." Inspection Procedure O-2
- The voltmeter needle does not fluctuate when the driver's seat belt is unfastened: Refer to Inspection Procedure O-7 "The driver's seat belt switch signal is not sent to the ETACS-ECU." Inspection Procedure O-7