Inspection Procedure J-4

Headlight Relay (low Drive Circuit:

Headlight Relay (high) Drive Circuit:

CIRCUIT OPERATION
If the column switch sends the passing switch ON signal to the front-ECU, the front-ECU switches the headlights from low-beam to high-beam or vice versa.

TECHNICAL DESCRIPTION (COMMENT)
If the headlights (low-beam and high-beam) are defective, 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.
If the headlights (low-beam and high-beam) do not illuminate normally, solve the problem first.
If the headlights (low-beam and high-beam) illuminate normally, go to Step 2.

STEP 2. Check the input signal.
Check the input signal from the passing switch.






CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "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.





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.
If a defect appears, check the passing switch input circuit.
Refer to Inspection Procedure O-17.
If no defect appears, replace the front-ECU.
The passing switch should work normally.