Inspection Procedure B-1

Tone alarm: Ignition key reminder tone alarm function does not work normally.

TECHNICAL DESCRIPTION (COMMENT)
The ETACS-ECU operates the ignition key reminder tone alarm function, based on input signals from the following switches:
- Ignition switch (IG1)
- Key reminder switch
- Driver's door 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 key reminder switch
- Malfunction of the driver's door 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 the ETACS-ECU power supply circuit.
If the ignition switch is at "LOCK" (OFF) position, do all of the following functions operate?
- Light reminder tone alarm function
- Central door locking system
- Hazard warning light
- interior light dimming function
- Theft-alarm system

Q: Does any function described above operate?

YES: Go to Step 2 or 3 .
NO: Check the ETACS-ECU battery circuit. Refer to Inspection Procedure P-1.

STEP 2. Check the input signal (by using scan tool MB991502).
Check the input signals from the following switches:
- Ignition switch (IG1)
- key reminder switch
- Driver's door 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 ignition key reminder 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)
- key reminder switch
- Driver's door 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 ignition key reminder tone alarm function should work normally.
NO: Check the relevant input circuit.