Inspection Procedure J-4

Headlight, taillight: Headlights do not illuminate when the passing switch is operated.

TECHNICAL DESCRIPTION (COMMENT)
If the column switch or the front-ECU is suspected to be defective.

TROUBLESHOOTING HINTS
- Malfunction of the column switch (turn-signal light and lighting switch)
- Malfunction of the front-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 headlight (low-beam and high-beam) operation.

Q: Do the headlights (low-beam and high-beam) illuminate 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 signal from the passing 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 M6991502.

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 front-ECU. The passing switch should work normally.
NO: Check the passing switch input circuit. Refer to Inspection Procedure O-15.

STEP 3. Check the input signal (by using a voltmeter).
Check the input signal from the passing 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 front-ECU. The passing switch should work normally.
NO: Check the passing switch input circuit. Refer to Inspection Procedure O-15.