Inspection Procedure J-5

Headlight, taillight: Headlight automatic shutdown function does not work normally.

TECHNICAL DESCRIPTION (COMMENT)
The ETACS-ECU and front-ECU operates the headlight automatic shutdown function, based on the signals from the following switches:
- Ignition switch (IG1)
- Taillight switch
- Headlight switch

If the function does work normally, a defect on relevant input circuits, the ETACS-ECU or the front ECU is suspected.

TROUBLESHOOTING HINTS
- Malfunction of the column switch (turn-signal light and lighting switch)
- Malfunction of the ETACS-ECU
- 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 DTC.

Q: Does the DTC set when the ignition switch is turned to the "LOCK" (OFF) position?

YES: Carry out the troubleshooting by referring to Diagnostic Trouble Code Chart.
NO: Go to Step 2 or 3 .

STEP 2. Check the input signal (by using scan tool MB991502).
Check the input signals from the following switches.
- Ignition switch (IG1)
- Taillight switch
- Headlight 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: Go to Step 4.
NO: Check the relevant input signal circuit.

STEP 3. Check the input signal (by using a voltmeter).
Check the input signals from the following switches.
- Ignition switch (IG1)
- Taillight switch
- Headlight 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: Go to Step 4.
NO: Check the relevant input signal circuit.

STEP 4. Replacement of ECU.
1. Replace the front-ECU.
2. The headlight automatic shutdown function should work normally.

Q: Is the headlight automatic shutdown function working normally?

YES: There is no action to be taken.
NO: Replace the ETACS-ECU. The headlight automatic shutdown function should work normally.