Inspection Procedure N-4

Theft-alarm system: Panic alarm function does not work.

TECHNICAL DESCRIPTION (COMMENT)
If the keyless entry system is normal, the ETACS-ECU is defective.

TROUBLESHOOTING HINTS
- 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 keyless entry system.

Q: Does the keyless entry system work normally?

YES: Go to Step 2 or 3.
NO: Solve the problem first.

STEP 2. Check the input signal (by using scan tool MB991502).
Check the input signals from the transmitter "PANIC" 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 panic alarm should work normally.
NO: Check the transmitter input signal circuit. Refer to Inspection Procedure O-18.

STEP 3. Check the input signal (by using a voltmeter).
Check the input signals from the transmitter "PANIC" 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 panic alarm should work normally.
NO: Check the transmitter input signal circuit. Refer to Inspection Procedure O-18.