Inspection Procedure O-3

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

Fog Light Switch Input Circuit Part 1:

Fog Light Switch Input Circuit Part 2:

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
- The fog light switch 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:
- 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 fog light switch connector C-76 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

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

YES: Go to Step 2.

NO: Repair or replace the damaged component(s). 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 2. 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 3.

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 3. Check the ground circuit to the fog light switch. Measure the resistance at fog light switch connector C-76.




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




2. Measure the resistance value between terminal 7 and ground.
- The resistance should equal 2 ohms or less.

Q: Is the measured resistance 2 ohms or less?

YES: Go to Step 5.

NO: Go to Step 4.




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

NOTE: Also check joint connector C-78 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-78 is damaged, repair or replace the damaged component(s) 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 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. If the for light switch operates normally, it indicates that a correct signal is sent from the fog light switch.




STEP 5. Check ETACS-ECU connector C-118 for damage.

Q: Is 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: 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. If the for light switch operates normally, it indicates that a correct signal is sent from the fog light switch.