Inspection Procedure L-1
INSPECTION PROCEDURE L-1: Fog Light: Fog lights do not illuminate when the fog light switch is turned on.
Connectors:
CIRCUIT OPERATION
-5Ghen 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 wiring harness between the defective light and the fog light relay may be defective. In this case, check the relevant circuit by referring to Fog Light. Diagrams
TROUBLESHOOTING HINTS
- The fog light switch may be defective
- The front-ECU may be defective
- The ETACS-ECU may be defective
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
DIAGNOSIS
Required Special Tools:
- MB001223: Test Harness Set
- MB991502: Scan Tool (MUT-II)
- MB991529: Diagnostic Trouble Code Check Harness
STEP 1. Verify the taillights and headlight operation.
Q: Do the taillights and headlights illuminate normally?
YES : Go to Step 2
NO : Solve the problem first. Diagnosis By Symptom
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 : Scan tool MB991502 does not sound when the fog light switch is turned from "OFF" to "ON": Refer to Inspection Procedure O-5 "The fog light switch signal is not sent to the ETACS-ECU. 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 : The voltmeter needle does not fluctuate when the fog light switch is turned from "OFF" to "ON": Refer to Inspection Procedure O-5 "The fog light switch signal is not sent to the ETACS-ECU. 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 the fog light relay. The fog lights should illuminate normally.
STEP 5. Check the power supply circuit to the fog light relay. Test at fog light relay connector A-04X.
1. Disconnect the fog light relay connector A-04X and measure the voltage available at the relay box side of the connector.
2. Measure the resistance value between terminal 1 and ground, and also between terminal 2 and ground.
- The voltage should equal approximately 12 volts (battery positive voltage).
Q: Is the measured voltage approximately 12 volts (battery positive voltage)?
YES : Go to Step 8.
NO : Go to Step 6.
STEP 6. Check the fog light relay connector A-04X for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is fog light relay connector A-04X in good condition?
YES : Go to Step 7.
NO : Repair or replace the damaged components). Refer to Harness Connector Inspection. Diagnostic AidsThe fog lights should illuminate normally.
STEP 7. Check the wiring harness between fog light relay connector A-04X (terminal 1 and 2) and battery.
Q: Is the wiring harness between fog light relay connector A-04X (terminal 1 and 2) and battery in good condition?
YES : No action is necessary and testing is complete.
NO : The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. The fog lights should illuminate normally.
STEP 8. Check the fog light relay connector A-04X and front-ECU connector A-10X for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are fog light relay connector A-04X and front-ECU connector A-10X in good condition?
YES : Go to Step 9.
NO : Repair or replace the damaged components). Refer to Harness Connector Inspection. Diagnostic AidsThe fog lights should illuminate normally.
STEP 9. Check the wiring harness between fog light relay connector A-04X (terminal 3) and front-ECU connector A-10X (terminal 1).
Q: Is the wiring harness between fog light relay connector A-04X (terminal 3) and front-ECU connector A-10X (terminal 1) in good condition?
YES : Go to Step 10.
NO : The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. The fog lights should illuminate normally.
STEP 10. Check the fog light connectors A-27 and A-31 and combination meter connector C-101 for loose, corroded or damaged terminals, or
terminals pushed back in the connector.
Q: Are fog light connectors A-27 and A-31 and combination meter connector C-101 in good condition?
YES : Go to Step 11.
NO : Repair or replace the damaged component(s). Refer to Harness Connector Inspection. Diagnostic AidsThe fog lights should illuminate normally.
STEP 11. Check the wiring harness between fog light relay connector A-04X (terminal 4) and fog light connectors A-27 (terminal 2) and A-31 (terminal 2) and combination meter connector C-101 (terminal 2).
NOTE: Also check intermediate connectors C-05 and C-209 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connectors C-05 or C-209 are damaged, repair or replace the damaged components) Refer to Harness Connector Inspection.
Q: Are the wiring harness between fog light relay connector A-04X (terminal 4) and fog light connectors A-27 (terminal 2) and A-31 (terminal 2) and combination meter connector C-103 (terminal 2) in good condition?
YES : Go to Step 12.
NO : The wiring harness may be damaged or the connector(s) may have loose, corroded or damaged terminals, or terminals pushed back in the connector. Repair the wiring harness as necessary. 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 : No action is necessary and testing is complete.
NO : Replace the ETACS-ECU. The fog light should illuminate normally.