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
- Malfunction of the 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)
- MB991529: Diagnostic Trouble Code Check Harness

STEP 1. Check 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: Check the relevant input circuit.

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: Check the relevant input circuit.