Page 23 of 1500

SWS DIAGNOSIS
SIMPLIFIED WIRING SYSTEM (SWS)54B-23
For checking item "HEADLAMP HI", the diagnostic 
tool MB991958 (MUT-III Sub Assembly) displays 
"OFF" on the item No.2 "DIMMER SW" when the 
headlamps are at high-beam. Therefore, the 
diagnostic tool MB991958 (MUT-III Sub Assembly) 
should display "ON" momentarily when the dimmer 
switch is operated.
.
TURN SIGNAL
.
BUZZER
NOTE:  The headlamp automatic shutoff function 
operates approximately one second after the lighting 
monitor tone alarm starts sounding, and then the 
tone alarm ceases sounding.
.
ITEM ITEM NO. INPUT SIGNAL DISPLAY ON 
DIAGNOSTIC TOOLNORMAL CONDITION
TURN-SIG.LH 10 Turn-signal lamp 
switch (RH)T/S RH SW (COLUMN 
ECU)OFF
11 Tu r n - s i g n a l   l a m p  
switch (LH)T/S LH SW (COLUMN 
ECU)ON
30 Ignition switch 
(IG1)IG SW (IG1) (ETACS ECU) ON
TURN-SIG.RH 10 Turn-signal lamp 
switch (RH)T/S RH SW (COLUMN 
ECU)ON
11 Tu r n - s i g n a l   l a m p  
switch (LH)T/S LH SW (COLUMN 
ECU)OFF
30 Ignition switch 
(IG1)IG SW (IG1) (ETACS ECU) ON
ITEM ITEM NO. INPUT SIGNAL DISPLAY ON DIAGNOSTIC 
TOOLNORMAL CONDITION
LGT 
MONI.ALRM00 Headlamp switch
HEADLAMP SW (COLUMN 
ECU)Either is ON
01 Tail lamp switch TAILLAMP SW (COLUMN 
ECU)
30 Ignition switch 
(IG1)IG SW (IG1) (ETACS ECU) OFF
32 Front door switch FRONT DOOR SW (ETACS 
ECU)ON
35 Headlamp 
automatic shutoff 
functionH/L AUTO-CUT (ETACS 
ECU)OFF
43 Tone alarm BUZZER (ETACS ECU) ON
OTHER 
ALARM30 Ignition switch 
(IG1)IG SW (IG1) (ETACS ECU) ON
43 Tone alarm BUZZER (ETACS ECU) ON 
         
        
        
     
        
        Page 24 of 1500

SWS DIAGNOSIS
SIMPLIFIED WIRING SYSTEM (SWS)54B-24
SUNROOF
PULSE CHECK
M1549015100562
1. The input signals (signals other than SWS 
communication line signals), which are 
compatible with the SWS monitor by using the 
diagnostic tool MB991958 (MUT-III Sub 
Assembly) or voltmeter, can be confirmed by the 
Pulse Check.2. Use the diagnostic tool MB991958 (MUT-III Sub 
Assembly) or voltmeter to check the following 
input signals.
NOTE:  If a problem is found in the Pulse Check, 
refer to Input Signal Chart P.54B-61.
Switches and their conditions, which are applicable 
for Pulse CheckITEM ITEM NO. INPUT SIGNAL DISPLAY ON 
DIAGNOSTIC TOOLNORMAL CONDITION
SUNROOF 
OPE.30 Ignition switch 
(IG1)IG SW (IG1) (ETACS ECU) ON
72 Response by the 
sunroof-ECUS/R ECU ACK (SUNROOF 
ECU)INPUT CHECK (only 
momentarily when switch is 
operated)
INPUT SIGNAL REQUIREMENTS FOR SOUNDING TONE 
ALARM
Key reminder switch When the ignition key is pulled out
Hazard warning lamp switch When the switch is turned from off to on
Door switches A door is opened when all the doors are 
closed
Door lock key cylinder switch When a door is locked or unlocked by a key 
cylinder
Door lock actuators Move the door lock knob from lock position 
to unlock position or vice versa
Door lock switch (incorporated in the power window main 
switch and front power window sub switch)When a door is locked or unlocked by a door 
lock switch
Keyless entry transmitter When the switch is turned from off to on
Interior lamp loaded signal Illuminates the interior lamps 
         
        
        
     
        
        Page 26 of 1500

DIAGNOSTIC TROUBLE CODE PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-26
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: Probe Harness
STEP 1. 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 2.
NO : Repair the CAN bus line (Refer to GROUP 54C, 
Diagnosis P.54C-5). 
         
        
        
     
        
        Page 27 of 1500
DIAGNOSTIC TROUBLE CODE PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-27
STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?
YES : Go to Step 3.
NO : There is an intermittent malfunction such as poor 
engaged connector(s) or open circuit (Refer to 
GROUP 00, How to Cope with Intermittent 
Malfunction P.00-14). 
         
        
        
     
        
        Page 28 of 1500

DIAGNOSTIC TROUBLE CODE PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-28
STEP 3. Use diagnostic tool MB991958 to select "ECU 
COMM Check" on the SWS monitor display. 
Check the following ECUs:
ETACS-ECU
Column switch (column-ECU)
Front-ECU
Sunroof-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" menus for the "ETACS ECU", 
"COLUMN ECU", "FRONT ECU" and "SUNROOF ECU" 
menus.
Q: Are "OK" displayed for the "ETACS ECU," "COLUMN 
ECU," "FRONT ECU" and "SUNROOF ECU" menus?
"OK" are displayed for all the items : It is determined that 
there is an intermittent malfunction such as poor 
engaged connector(s) or open circuit (Refer to 
GROUP 00, How to Cope with Intermittent 
Malfunction P.00-14).
"NG" is displayed for the "ETACS ECU" menu : Refer to 
Inspection Procedure A-3 "Communication with the 
ETACS-ECU is not possible P.54B-74."
"NG" is displayed for the "COLUMN ECU" menu : Refer 
to Inspection Procedure A-2 "Communication with the 
column switch (column-ECU) is not possible 
P.54B-68."
"NG" is displayed for the "FRONT ECU" menu : Refer to 
Inspection Procedure A-4 "Communication with the 
front-ECU is not possible P.54B-80."
"NG" is displayed for the "SUNROOF ECU" menu : 
Refer to Inspection Procedure A-5 "Communication 
with the sunroof-ECU is not possible P.54B-87." 
         
        
        
     
        
        Page 30 of 1500

DIAGNOSTIC TROUBLE CODE PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-30
STEP 1. 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 2.
NO : Repair the CAN bus line (Refer to GROUP 54C, 
Diagnosis P.54C-5).
STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?
YES : Go to Step 3.
NO : There is an intermittent malfunction such as poor 
engaged connector(s) or open circuit (Refer to 
GROUP 00, How to Cope with Intermittent 
Malfunction P.00-14). 
         
        
        
     
        
        Page 31 of 1500

DIAGNOSTIC TROUBLE CODE PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-31
STEP 3. Use diagnostic tool MB991958 to select "ECU 
COMM Check" on the SWS monitor display. 
Check the following ECUs:
Column-ECU
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" menus for both the "COLUMN ECU" 
and the "ETACS ECU" menus.
Q: Are "OK" displayed for both the "COLUMN ECU" and 
"ETACS ECU" menus?
"OK" are displayed for all the items : It is determined that 
there is an intermittent malfunction such as poor 
engaged connector(s) or open circuit (Refer to 
GROUP 00, How to Cope with Intermittent 
Malfunction P.00-14).
"NG" is displayed for the "COLUMN ECU" menu : Refer 
to Inspection Procedure A-2 "Communication with the 
column switch (column-ECU) is not possible 
P.54B-68."
"NG" is displayed for the "ETACS ECU" menu : Refer to 
Inspection Procedure A-3 "Communication with the 
ETACS-ECU is not possible P.54B-74." 
         
        
        
     
        
        Page 33 of 1500

DIAGNOSTIC TROUBLE CODE PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-33
STEP 1. 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 2.
NO : Repair the CAN bus line (Refer to GROUP 54C, 
Diagnosis P.54C-5).
STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?
YES : Go to Step 3.
NO : There is an intermittent malfunction such as poor 
engaged connector(s) or open circuit (Refer to 
GROUP 00, How to Cope with Intermittent 
Malfunction P.00-14).