Inspection Procedure O-3

The ETACS-ECU does not Receive Any Signal from the Fog Light Switch.

Fog Light Switch Input Circuit:

CIRCUIT OPERATION
The ETACS-ECU operates the fog lights according to signal from the fog light switch.

TECHNICAL DESCRIPTION (COMMENT)
If the signal is not normal, the fog lights do not work normally. If the signal is not normal, the fog light switch or the ETACS-ECU may be defective.

TROUBLESHOOTING HINTS
- Malfunction of the fog light switch
- Malfunction of the ETACS-ECU
- Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Test Harness Set
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicles communication interface
- MB991827: MUT-III USB cable
- MB991911: MUT-III Main harness B







STEP 1. Check the fog light switch.
Remove the fog light switch. Then check continuity between the switch terminals.

Q: Is the fog light switch in good condition?

YES: Go to Step 2.

NO: Repair the fog light switch. If the for light switch operates normally, it indicates that a correct signal is sent from the fog light switch.

STEP 2. Measure at fog light switch connector C-76 in order to check the ground circuit to the fog light switch.




1. Disconnect fog light switch connector C-76, and measure at the wiring harness side.




2. Measure the resistance value between terminal 7 and ground.
- The measured value should be 2 ohm or less.

Q: Does the measured resistance value correspond with this range?

YES: Go to Step 5.

NO: Go to Step 3.




STEP 3. Check fog light switch connector C-76 for damage.

Q: Is fog light switch connector C-76 in good condition?

YES: Go to Step 4.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. Repair the fog light switch. If the for light switch operates normally, it indicates that a correct signal is sent from the fog light switch.




STEP 4. Check the wiring harness between fog light switch connector C-76 (terminal 7) and ground.

NOTE: Also check joint connector C-78. If joint connector C-78 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between fog light switch connector C-76 (terminal 7) and the ground in good condition?

YES: No action to be taken.

NO: Repair the wiring harness. If the for light switch operates normally, it indicates that a correct signal is sent from the fog light switch.







STEP 5. Check fog light switch connector C-76 and ETACS-ECU connector C-118 for damage.

Q: Are fog light switch connector C-76 and ETACS-ECU connector C-118 in good condition?

YES: Go to Step 6.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. If the for light switch operates normally, it indicates that a correct signal is sent from the fog light switch.







STEP 6. Check the wiring harness between fog light switch connector C-76 (terminal 6) and ETACS-ECU (terminal 54) connector C-118.

Q: Is the wiring harness between fog light switch connector C-76 (terminal 6) and ETACS-ECU connector C-118 (terminal 54) in good condition?

YES: Replace the ETACS-ECU. If the for light switch operates normally, it indicates that a correct signal is sent from the fog light switch.

NO: Repair the wiring harness. If the for light switch operates normally, it indicates that a correct signal is sent from the fog light switch.