Page 345 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-345
INSPECTION PROCEDURE J-2: Fog Light: Fog lamps do not go out when the headlamps (low-beam)
are turned off while the fog lamps are on.
.
TECHNICAL DESCRIPTION (COMMENT)
If the trouble above occurs, the front-ECU may be
defective.
.
TROUBLESHOOTING HINT
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
The front-ECU may be defective
DIAGNOSIS
Replace the front-ECU.
The fog lamps should go out when the headlamps (low-beam)
are turned off while the fog lamps are on.
INSPECTION PROCEDURE J-3: Fog Light: One of the fog lamps does not illuminate.
.
TECHNICAL DESCRIPTION (COMMENT)
If one of the fog lamps does not illuminate, the fog
lamp relay or the fog lamp bulb may be defective. If
the fog lamp indicator lamp does not illuminate, the
combination meter may be defective.
.
TROUBLESHOOTING HINTS
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
The wiring harness or connectors may have
loose, corroded, or damaged terminals, or termi-
nals pushed back in the connector
The fog lamp bulb may be defective
.
DIAGNOSIS
Required Special Tool:
MB991223: Harness Set
Page 346 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-346
STEP 1. Verify that the fog lamps and the fog lamp
indicator lamp illuminate.
Q: Do the fog lamps and the fog lamp indicator lamp
illuminate normally?
Only the fog lamp (LH) does not illuminate : Go to Step
2.
Only the fog lamp (RH) does not illuminate : Go to Step
8.
Only the fog lamp indicator does not illuminate : Refer
to Inspection Procedure J-4 "The fog lamp indicator
does not illuminate normally P.54B-350."
Both of the fog lamps do not illuminate : Refer to
Inspection Procedure J-1 "Fog lamps do not
illuminate when the fog lamp switch is turned on
P.54B-340."
STEP 2. Check fog lamp (LH) connector A-22 for loose,
corroded or damaged terminals, or terminals pushed back
in the connector.
Q: Is fog lamp (LH) connector A-22 in good condition?
YES : Go to Step 3.
NO : Repair or replace the damaged component(s). Refer
to GROUP 00E, Harness Connector Inspection
P.00E-2. Check that the fog lamps illuminate
normally.
STEP 3. Check the fog lamp bulb (LH).
(1) Remove the fog lamp bulb (LH).
(2) Verify that the fog lamp bulb (LH) is not damaged or burned
out.
Q: Is the fog lamp bulb (LH) in good condition?
YES : Go to Step 4.
NO : Replace the fog lamp bulb (LH). Verify that the fog
lamps illuminate normally.
Page 347 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-347
STEP 4. Check the ground circuit to the fog lamp (LH).
Measure the resistance at fog lamp (LH) connector A-22.
(1) Disconnect fog lamp (LH) connector A-22 and measure the
resistance available at the wiring harness side of the
connector.
(2) Measure the resistance value between terminal 2 and
ground.
The resistance should be 2 ohms or less.
Q: Is the measured resistance 2 ohms or less?
YES : Go to Step 6.
NO : Go to Step 5.
STEP 5. Check the wiring harness between fog lamp (LH)
connector A-22 (terminal 2) and ground.
Q: Is the wiring harness between fog lamp (LH) connector
A-22 (terminal 2) and 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. Verify that
the fog lamps illuminate normally.
STEP 6. Check fog lamp relay connector A-05X for loose,
corroded or damaged terminals, or terminals pushed back
in the connector.
Q: Is fog lamp relay connector A-05X in good condition?
YES : Go to Step 7.
NO : Repair or replace the damaged component(s). Refer
to GROUP 00E, Harness Connector Inspection
P.00E-2. Check that the fog lamps illuminate
normally.
Page 348 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-348
STEP 7. Check the wiring harness between fog lamp relay
connector A-05X (terminal 4) and fog lamp (LH) connector
A-22 (terminal 1).
Q: Is the wiring harness between fog lamp relay connector
A-05X (terminal 4) and fog lamp (LH) connector A-22
(terminal 1) 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. Verify that
the fog lamps illuminate normally.
STEP 8. Check fog lamp (RH) connector A-28 for loose,
corroded or damaged terminals, or terminals pushed back
in the connector.
Q: Is fog lamp (RH) connector A-28 in good condition?
YES : Go to Step 9.
NO : Repair or replace the damaged component(s). Refer
to GROUP 00E, Harness Connector Inspection
P.00E-2. Check that the fog lamps illuminate
normally.
STEP 9. Check the fog lamp bulb (RH).
(1) Remove the fog lamp bulb (RH).
(2) Verify that the fog lamp bulb (RH) is not damaged or burned
out.
Q: Is the fog lamp bulb (RH) in good condition?
YES : Go to Step 10.
NO : Replace the fog lamp bulb (RH). Verify that the fog
lamps illuminate normally.
Page 349 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-349
STEP 10. Check the ground circuit to the fog lamp (RH).
Measure the resistance at fog lamp (RH) connector A-28.
(1) Disconnect fog lamp (RH) connector A-28 and measure the
resistance available at the wiring harness side of the
connector.
(2) Measure the resistance value between terminal 2 and
ground.
The resistance should be 2 ohms or less.
Q: Is the measured resistance 2 ohms or less?
YES : Go to Step 12.
NO : Go to Step 11.
STEP 11. Check the wiring harness between fog lamp (RH)
connector A-28 (terminal 2) and ground.
Q: Is the wiring harness between fog lamp (RH) connector
A-28 (terminal 2) and 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. Verify that
the fog lamps illuminate normally.
STEP 12. Check fog lamp relay connector A-05X for loose,
corroded or damaged terminals, or terminals pushed back
in the connector.
Q: Is fog lamp relay connector A-05X in good condition?
YES : Go to Step 13.
NO : Repair or replace the damaged component(s). Refer
to GROUP 00E, Harness Connector Inspection
P.00E-2. Check that the fog lamps illuminate
normally.
Page 350 of 1500
SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-350
STEP 13. Check the wiring harness between fog lamp relay
connector A-05X (terminal 4) and fog lamp (RH) connector
A-28 (terminal 1).
Q: Is the wiring harness between fog lamp relay connector
A-05X (terminal 4) and fog lamp (RH) connector A-28
(terminal 1) 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. Verify that
the fog lamps illuminate normally.
INSPECTION PROCEDURE J-4: The fog lamp indicator does not illuminate normally.
NOTE: This troubleshooting procedure requires the
use of Diagnostic Tool MB991958 and SWS monitor
kit MB991813. For details on how to use the SWS
monitor, refer to "How to connect SWS monitor
P.54B-13."
.
Page 351 of 1500
SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-351
CIRCUIT OPERATION
At the same time that the fog lamps are illuminated,
the ETACS-ECU sends a signal to illuminate the fog
lamp indicator via the CAN bus line.
.
TECHNICAL DESCRIPTION (COMMENT)
If the fog lamp indicator does not illuminate normally,
connector(s), wiring harness in the CAN bus lines,
the ETACS-ECU or the combination meter may be
defective.
.
TROUBLESHOOTING HINTS
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
Trouble in input signal system
The wiring harness or connectors may have
loose, corroded, or damaged terminals, or termi-
nals pushed back in the connector
The combination meter may be defective
The ETACS-ECU may be defective
.
Page 352 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-352
DIAGNOSIS
Required Special Tools:
MB991223: Harness Set
MB991958: Diagnostic Tool (MUT-III Sub Assembly)
MB991824: Vehicle Communication Interface (V.C.I.)
MB991827: MUT-III USB Cable
MB991910: MUT-III Main Harness A
MB991813: SWS Monitor Kit
MB991806: SWS Monitor Cartridge
MB991812: SWS Monitor Harness (For Column-ECU)
MB991822: Test Probe Harness
STEP 1. Check the fog lamps.
When the fog lamp switch is operated, check that the fog lamps
illuminate/go off normally.
Q: Are the fog lamps operating properly?
YES : Go to Step 2.
NO : First, repair the fog lamps. Refer to Inspection
Procedure J-3 "One of the fog lamps does not
illuminate P.54B-345."
STEP 2. Using Diagnostic Tool MB991958, diagnose the
CAN bus line.
To prevent damage to Diagnostic Tool MB991958, always
turn the ignition switch to the "LOCK" (OFF) position
before connecting or disconnecting Diagnostic Tool
MB991958.
(1) Connect Diagnostic Tool MB991958. Refer to "How to
connect SWS monitor P.54B-13."
(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the CAN bus line found to be normal?
YES : Go to Step 3.
NO : Repair the CAN bus line (Refer to GROUP 54C,
Diagnosis P.54C-15).