Page 291 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-291
DIAGNOSIS
Required Special Tool:
MB991223: Harness Set
STEP 1. Check the headlamp operation.
Q: Which of the headlamps does not illuminate?
LH (low beam) : Go to Step 2.
RH (low beam) : Go to Step 6.
LH (only low-beam) : Go to Step 10.
RH (only low-beam) : Go to Step 13.
LH (only high beam) : Go to Step 16.
RH (only high beam) : Go to Step 21.
Low beam only (both RH and LH) : Refer to Inspection
Procedure H-2 "The headlamps (low-beam) do not
illuminate normally P.54B-264."
High beam only (both RH and LH) : Refer to Inspection
Procedure H-3 "The headlamps (high-beam) do not
illuminate normally P.54B-268."
High beam indicator lamp : Refer to Inspection Procedure
H-8 "The high-beam indicator lamp does not
illuminate P.54B-301."
STEP 2. Check headlamp (LH) connector A-20 for loose,
corroded or damaged terminals, or terminals pushed back
in the connector.
Q: Is headlamp (LH) connector A-20 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 headlamps illuminate
normally.
STEP 3. Check headlamp (LH) bulb.
(1) Remove the headlamp (LH) bulb.
(2) Verify that the headlamp (LH) bulb is not damaged or
burned out.
Q: Is headlamp (LH) bulb normal?
YES : Go to Step 4.
NO : Replace the headlamp (LH) bulb. Verify that the
headlamps illuminate normally.
Page 301 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-301
STEP 25. Check the wiring harness between headlamp
(RH) connector A-32 (terminals 5 and 1) and ground.
Q: Is the wiring harness between headlamp (RH) connector
A-32 (terminals 5 and 1) 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 headlamps illuminate normally.
INSPECTION PROCEDURE H-8: Headlamp and Taillamp: The High-beam indicator lamp does not
illuminate.
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."
.
CIRCUIT OPERATION
At the same time that the high beams are illumi-
nated, the ETACS-ECU sends a signal to illuminate
the high beam indicator via the CAN bus line.
.
TECHNICAL DESCRIPTION (COMMENT)
If the high beam indicator does not illuminate nor-
mally, 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
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 304 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-304
STEP 4. Use Diagnostic Tool MB991958 to select "ECU
COMM Check" on the SWS monitor display.
Check the ETACS-ECU.
Connect special tool MB991910 before connecting special
tool MB991812. Be sure to connect special tool MB991806
after turning on special tool MB991824.
(1) Connect the SWS monitor. Refer to "How to connect SWS
monitor P.54B-13."
(2) Turn the ignition switch to the "LOCK" (OFF) position.
(3) Operate Diagnostic Tool MB991958 according to the
procedure below to display "ECU COMM Check."
a. Select "Interactive Diagnosis."
b. Select "System select."
c. Select "SWS."
d. Select "SWS MONITOR."
e. Select "ECU COMM Check."
(4) Diagnostic Tool MB991958 should show "OK" on the "ECU
COMM Check" menu for the "ETACS ECU" menu.
Q: Is "OK" displayed for the "ETACS ECU" menu?
YES : Go to Step 5.
NO : Refer to Inspection Procedure A-3 "Communication
with the ETACS-ECU is not possible P.54B-74."
STEP 5. Replace the combination meter.
(1) Replace the combination meter.
(2) Check that the high beam indicator lamp illuminates
normally.
Q: Does the high beam indicator lamp illuminate normally?
YES : No action is necessary and testing is complete.
NO : Replace the ETACS-ECU. Check that the high beam
indicator lamp illuminates normally.
Page 339 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-339
FOG LAMP
GENERAL DESCRIPTION CONCERNING THE FOG LAMPSM1549021400216
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80The following ECUs affect the functions and control
of the fog lamps.
Fog lamp
The fog lamps will illuminate only when the fog lamp
switch is operated while the low-beam headlamps
are on.
The fog lamps will be switched off when any of the
following conditions is met. The fog lamps will also
be switched off automatically by headlamp automatic
shutoff function.
When the high-beam headlamps are switched
on, the fog lamps will be switched off. If the
low-beam headlamps are switched on again, the
fog lamps will illuminate again.
When the headlamp switch is turned off or the tail
lamps and headlamps are off, the fog lamps will
be switched off. If the low-beam headlamps are
switched on again, the fog lamps will not illumi-
nate again.
Fog lamp indicator
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. The combination meter receives the
transmitted signal and turns the fog lamp indicator on and off. FUNCTION CONTROL ECU
Fog lamp ETACS-ECU, front-ECU, column switch
Fog lamp indicator ETACS-ECU, column switch
Page 420 of 1500

INPUT SIGNAL PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-420
INSPECTION PROCEDURE M-5: Column Switch: ETACS-ECU does not receive any signal from the
taillamp switch, the headlamp switch, the passing lamp switch, the dimmer switch or the turn-signal
lamp switch.
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."
.
CIRCUIT OPERATION
The ETACS-ECU operates the following equipment
or functions according to signal from the column
switch (turn-signal lamp and lighting switch):
Light reminder tone alarm function
Turn-signal lamp buzzer
Headlamp
Turn-signal lamp
High-beam indicator
Turn-signal indicators
.
TECHNICAL DESCRIPTION (COMMENT)
If the signal is not normal, the equipment or functions
described in "CIRCUIT OPERATION" do not work
normally. If the signal is not normal, the column
switch (turn-signal lamp and lighting switch) or the
ETACS-ECU may be defective.
.
TROUBLESHOOTING HINTS
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
The column switch (turn-signal lamp and lighting
switch) may be defective
The ETACS-ECU may be defective
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
Page 484 of 1500

CHECK AT ECU TERMINAL
SIMPLIFIED WIRING SYSTEM (SWS)54B-484
FRONT-ECU
NOTE: Terminal voltages cannot be measured as the
front-ECU is installed directly on the relay box.
Therefore, this information is only for reference.
TERMINAL
NO.INSPECTION ITEM INSPECTION CONDITION NORMAL VALUE
1 Output to fog lamp relay When the fog lamps are on Battery positive voltage
2 Output to headlamp (high-beam) When headlights (high-beam)
are onBattery positive voltage
3, 4 Battery power supply (for
headlamp)Always Battery positive voltage
5 Battery power supply (for
taillamp)Always Battery positive voltage
6 Output to headlamp (low-beam) When headlights (low-beam) are
onBattery positive voltage
7 Battery power supply (for ECU) Always Battery positive voltage
8 Output to taillamps When taillamps are on Battery positive voltage
9
11
21 Output to windshield washer When windshield washer is on Battery positive voltage
22 SWS communication line Always 0
12 V (pulse signal)
23 Input of automatic stop signal to
windshield wiperWhen windshield wiper is on Battery positive voltage
24 Power supply to ignition switch
(ACC)Ignition switch: "ACC" Battery positive voltage
25 Input of backup signal from
headlamp switchHeadlamp switch: ON0 V
26 Input of backup signal to
windshield wiperWindshield low-speed wiper
switch or windshield high-speed
wiper switch: ON0 V
27 Output to windshield wiper
(low-speed)When windshield wiper is on (at
low speed)Battery positive voltage
28 Output to windshield wiper
(high-speed)When windshield wiper is on (at
high speed)Battery positive voltage
30 Power supply to ignition switch
(IG2)Ignition switch: "ON" Battery positive voltage
31 Ground Always 0 V
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