Page 54 of 1500

DIAGNOSTIC TROUBLE CODE PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-54
Past trouble
If DTC 021 (U1128) is stored as a past trouble,
carry out diagnosis with particular emphasis on
wiring and connector(s) in the CAN bus line
between the combination meter and the
ETACS-ECU, and the power supply system to the
combination meter. For diagnosis procedures,
refer to "How to cope with past trouble" (Refer to
GROUP 00, How to treat past trouble P.00-16).NOTE: You cannot find a past trouble, by the
MUT-III CAN bus diagnostics even if there is a
failure in CAN bus lines. In this case, refer to
GROUP 00, How to Cope with Intermittent Mal-
function P.00-14 and check the CAN bus lines.
You can narrow down the possible cause of the
trouble by referring to the DTC, which is set
regarding the CAN communication-linked ECUs
(Refer to GROUP 54C, CAN Bus Line Diagnos-
tics P.54C-6).
.
TROUBLESHOOTING HINTS
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
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 56 of 1500
DIAGNOSTIC TROUBLE CODE PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-56
STEP 4. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Turn the ignition switch to the "ON" position.
(2) Check if the DTC is set.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?
YES : Replace the ETACS-ECU. On completion, verify that
the DTC is not reset.
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 63 of 1500
SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-63
SYMPTOM PROCEDURES
INSPECTION PROCEDURE A-1: Communication with the SWS Monitor Kit is not Possible.
.
TECHNICAL DESCRIPTION (COMMENT)
The SWS monitor kit may be connected improperly.
.
TROUBLESHOOTING HINTS
The SWS monitor body (I/F cartridge) may be
defective
The SWS monitor harness may be defective
The wiring harness or connectors may have
loose, corroded, or damaged terminals, or termi-
nals pushed back in the connector
The ETACS-ECU may be defective
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
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
Page 64 of 1500
SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-64
STEP 1. Verify SWS monitor kit MB991813 for proper
connection.
Q: Is SWS monitor kit MB991813 connected with the
column switch properly?
YES : Go to Step 2.
NO : Connect SWS monitor kit MB991813 to the column
switch securely.
STEP 2. Verify the power supply circuit to the ETACS-ECU.
Q: Does the system communicate with diagnostic tool
MB991958 when the ignition switch is turned to the
"ON" position?
YES : Refer to Inspection Procedure A-3 "Communication
with the ETACS-ECU is not possible P.54B-74."
NO : Go to Step 3.
STEP 3. Check ETACS-ECU connectors C-218 and C-219
for loose, corroded or damaged terminals, or terminals
pushed back in the connector.
Q: Are ETACS-ECU connectors C-218 and C-219 in good
condition?
YES : Go to Step 4.
NO : Repair or replace the damaged component(s). Refer
to GROUP 00E, Harness Connector Inspection
P.00E-2. Verify that the system should communicate
with the SWS monitor normally.
Page 68 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-68
INSPECTION PROCEDURE A-2: Communication with the Column Switch (column-ECU) is not
Possible.
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 power supply to the column switch is pro-
vided by the battery and the ignition switch (IG1).
If the power supply system from the battery is
defective, the system operates by the power sup-
ply from the ignition switch (IG1).
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
.
TECHNICAL DESCRIPTION (COMMENT)
The power supply circuit to the column switch (col-
umn-ECU) may be defective. If the battery power
supply circuit (terminal 1 of the column switch) to the
ECU is damaged, also check the power supply circuit
from the ignition switch (IG1) (terminal 9 of the col-
umn switch), and repair if necessary.
.
TROUBLESHOOTING HINTS
The wiring harness or connectors may have
loose, corroded, or damaged terminals, or termi-
nals pushed back in the connector
The column 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: Probe Harness
Page 74 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-74
INSPECTION PROCEDURE A-3: Communication with the ETACS-ECU is not Possible.
.
CIRCUIT OPERATION
The power supply to the ETACS-ECU is provided
by the battery and the ignition switch (IG1).
If the power supply system from the battery is
defective, the system operates by the power sup-
ply from the ignition switch (IG1).
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
.
TECHNICAL DESCRIPTION (COMMENT)
It is suspected that the power supply circuit to the
ETACS-ECU is defective, or the wiring harness
between the SWS monitor kit and the ETACS-ECU
or their connector(s) is damaged. If the battery power
supply circuit to the ECU (terminal 20 of the ETACS-ECU) is damaged, also check the power
supply circuit from the ignition switch (IG1) (terminal
8 of the ETACS-ECU), and repair if necessary. If the
ground circuit to the ECU (terminal 3 of the
ETACS-ECU) is damaged, also check the ground cir-
cuit to the sensor (terminal 50 of the ETACS-ECU),
and repair if necessary.
.
TROUBLESHOOTING HINTS
The wiring harness or connectors may have
loose, corroded, or damaged terminals, or termi-
nals pushed back in the connector
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
Page 80 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-80
INSPECTION PROCEDURE A-4: Communication with the Front-ECU is not Possible.
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 power supply to the front-ECU is provided by
the battery and the ignition switch (IG2).
If the power supply system from the battery is
defective, the system operates by the power sup-
ply from the ignition switch (IG2).
Refer to circuit diagrams GROUP-90
Refer to configuration diagrams GROUP-80
.
TECHNICAL DESCRIPTION (COMMENT)
It is suspected that the power supply circuit to the
front-ECU is defective, or the wiring harness
between the SWS monitor kit and the front-ECU or
their connector(s) is damaged. If the battery power
supply circuit to the ECU (terminal 5 of the
front-ECU) is damaged, also check the power supply
circuit from the ignition switch (IG2) (terminal 22 of
the front-ECU), and repair if necessary.
.
TROUBLESHOOTING HINTS
The wiring harness or connectors may have
loose, corroded, or damaged terminals, or termi-
nals pushed back in the connector
The front-ECU may be defective
The ETACS-ECU may be defective
Page 88 of 1500

SYMPTOM PROCEDURES
SIMPLIFIED WIRING SYSTEM (SWS)54B-88
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
STEP 1. Check sunroof motor assembly connector D-04
for loose, corroded or damaged terminals, or terminals
pushed back in the connector.
Q: Is sunroof motor assembly connector D-04 in good
condition?
YES : Go to Step 2.
NO : Repair or replace the damaged component(s). Refer
to GROUP 00E, Harness Connector Inspection
P.00E-2. The system should communicate with the
sunroof-ECU normally.
STEP 2. Check the fusible link (5) line of power supply
circuit to the sunroof motor assembly. Measure the voltage
at sunroof motor assembly connector D-04.
(1) Disconnect sunroof motor assembly connector D-04 and
measure the voltage available at the wiring harness side of
the connector.
(2) Measure the voltage between terminal 1 and ground.
The voltage should measure approximately 12 volts
(battery positive voltage).
Q: Is the measured voltage approximately 12 volts (battery
positive voltage)?
YES : Go to Step 4.
NO : Go to Step 3.