Inspection Procedure L-1

Fog light: Fog lights do not illuminate when the fog light switch is turned on.

Fog Lights Drive Circuit:

Connectors:

CIRCUIT OPERATION
When the fog light switch is turned on while the front-ECU is illuminating the taillights or headlights (low-beam), the ETACS-ECU sends a 'light on' signal to the front-ECU, causing the front-ECU to illuminate the fog lights.

TECHNICAL DESCRIPTION (COMMENT)
If the taillights and headlights illuminate normally, the fog light relay, the fog light switch, the front-ECU or the ETACS-ECU may be defective.

NOTE: If only one of the fog lights or the fog light indicator light does not illuminate, the relevant bulb may be burned out or the harness wire between the defective light and the fog light relay may be defective. In this case, check the relevant circuit by referring to Fog Light.

TROUBLESHOOTING HINTS
- Malfunction of the fog light relay
- Malfunction of the fog light switch
- Malfunction of the front-ECU
- 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 taillights and headlight operation.

Q: Do the taillights and headlights 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 signals from the fog light 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 fog light input signal circuit. Refer to Inspection Procedure O-5.

STEP 3. Check the input signal (by using a voltmeter).
Check the input signals from the fog light 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 fog light input signal circuit. Refer to Inspection Procedure O-5.

STEP 4. Check the fog light relay.

Q: Is the fog light relay in good condition?

YES: Go to Step 5.
NO: Replace it. The fog lights should illuminate normally.

STEP 5. Check the fog light relay power supply circuit at the fog light relay connector A-06X.
1. Disconnect the fog light relay connector A-06X and measure at the relay box side.

2. Measure the voltages between terminal 1, 4 and ground.

Q: Are the voltages approximately 12 volts (battery positive voltage)?

YES: Go to Step 8.
NO: Go to Step 6.

STEP 6. Check fog light relay connector A-06X for damage.

Q: Is fog light relay connector A-06X In good condition?

YES: Go to Step 7.
NO: Repair or replace it. Refer to Harness Connector Inspection. The fog lights should illuminate normally.

STEP 7. Check the harness wire between fog light relay connector A-06X and battery.

Q: Is the harness wire between fog light relay connector A-06X and battery in good condition?

YES: There is no action to be taken.
NO: Repair it. The fog lights should illuminate normally.

STEP 6. Check fog light relay connector A-06X and front-ECU connector A-09X for damage.

Q: Are fog light relay connector A-06X and front-ECU connector A-09X in good condition?

YES: Go to Step 9.
NO: Repair or replace them. Refer to Harness Connector Inspection. The fog lights should illuminate normally.

STEP 9. Check the harness wire between fog light relay connector A-06X and front-ECU connector A-09X.

Q: Is the harness wire between fog light relay connector A-06X and front-ECU connector A-09X in good condition?

YES: Go to Step 10.
NO: Repair it. The fog lights should illuminate normally.

STEP 10. Check fog light connectors A-27 and A-31 and combination meter connector C-103 for damage.

Q: Are fog light connectors A-27 and A-31 and combination meter connector C-103 in good condition?

YES: Go to Step 11.
NO: Repair or replace them. Refer to Harness Connector Inspection. The fog lights should illuminate normally.

STEP 11. Check the harness wires between fog light relay connector A-06X and fog light connectors A-27 and A-31 and combination meter connector C-103.

NOTE: After checking intermediate connectors C-05 and C-209, check the wires. If intermediate connectors C-05 and C-209 are damaged, repair or replace them. Refer to Harness Connector Inspection.

Q: Are the harness wires between fog light relay connector A-06X and fog light connectors A-27 and A-31 and combination meter connector C-103 in good condition?

YES: Go to Step 12.
NO: Repair them. The fog lights should illuminate normally.

STEP 12. Replacement of ECU
1. Replace the front-ECU.
2. The fog lights should illuminate normally.

Q: Do the fog lights illuminate normally?

YES: There is no action to be taken.
NO: Replace the ETACS-ECU. The fog light should illuminate normally.