Acura RSX Honda Integra. Manual — part 462
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S6M6A00J00050600000CAAT00
Multiplex Communication
Wake-up and Sleep
Fail-safe
22-188
Multiplex Control System
System Description
The multiplex control system has four internal
functions:
• Multiplexing (sends multiple signals over shared
wires)
• Wake up/sleep (runs at full power only on demand to
reduce battery draw)
• Fail-safe (fixes or ignores faulty signals)
• Self-diagnosis (Mode 1 for the system, Mode 2 for
input lines)
The system controls the function of these circuits:
• Entry light control (ignition key light and ceiling light)
• Wiper/washer (intermittent wipe and park functions)
• Interlock system
• Keyless/power door lock
• Gauge assembly, temperature gauge, and indicator
lights
• HVAC (compressor and fan control)
• Key-in reminder
• Lights-on reminder
• Seat belt reminder
To reduce the number of wire harnesses, digital signals
are sent via shared multiplex communication lines
rather than sending normal electrical signals through
individual wires.
• The input signals from each switch are converted to
digital signals at the central processing unit (CPU).
• The digital signals are sent from the transmitting unit
to the receiving unit as serial signals.
• The transmitted signal is converted to a switch signal
at the receiving unit, and it operates the related
component or monitors a switch.
• There are exclusive communication lines between
the ECM/PCM, the gauge assembly, the keyless
control unit, and the under-dash fuse/relay box.
The multiplex control system has ‘‘wake-up’’ and
‘‘sleep’’ functions to decrease parasitic draw on the
battery when the ignition switch is OFF.
• In the sleep mode, the multiplex control unit stops
functioning (communication and CPU control) when it
is not necessary for the system to operate.
• As soon as any operation is requested (for example, a
door is unlocked), the related control unit in the sleep
mode immediately wakes up and begins to function.
• When the ignition switch is turned OFF, and the
driver’s or front passenger’s door is opened, then
closed, there is about a 40 second delay before the
control unit goes from the wake-up mode to the sleep
mode.
• If any door is open, the sleep mode will not function.
• If a key is in the ignition switch, the sleep mode will
not function.
• When in sleep mode, the draw is reduced from
70
80 mA to less than 10 mA.
To prevent improper operation, the multiplex control
system has a fail-safe function. In the fail-safe mode,
the output signal is fixed when any part of the system
malfunctions (for example; a faulty control unit or
communication line).
Each control unit has a hardware fail-safe function that
fixes the output signal when there is any CPU
malfunction, and a software fail-safe function that
ignores the signal from the malfunctioning control unit
and allows the system to operate normally.
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S6M6A00J00050600000FAAT21
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Special Tools Required
YES
NO
YES
NO
YES
NO
YES
NO
Mode 1 Test
22-189
Troubleshooting
B
A
MODE 1: Ignition key light and ceiling light
2 sec.
0.2 sec.
0.2 sec.
OFF
ON
MPCS service connector 07WAZ-001010A
NOTE: Check for ECM/PCM DTC(s). Troubleshoot and
repair the cause for the DTC(s) first.
1. Remove the driver’s dashboard lower cover
(see page 20-63).
2. Check the No. 9 (10 A) fuse in the under-hood fuse/
relay box and the No. 10 (7.5 A) fuse in the under-
dash fuse/relay box.
Go to step 3.
Find and repair the cause of the blown fuse.
3. Turn the ignition switch ON (II).
If the driver’s seat belt is unbuckled, the seat belt
reminder will beep 6 times.
4. Set the ceiling light to the middle position and close
all the doors.
5. Connect the special tool (A) to the multiplex
inspection connector (B).
6. After about 5 seconds, the ignition key light and
ceiling light should come on for 2 seconds, go out ,
then blink on for 0.2 second to show the system is
now in Mode 1.
Go to step 8.
Go to step 7.
7. Check for continuity between the No. 4 terminal of
the under-dash fuse/relay box connector J and
body ground.
Replace the under-dash fuse/relay box.
Repair the open in the wire. If the wire is OK,
repair G301.
8. If there are any DTCs present, the ignition key light
and ceiling light will blink to indicate the DTC(s). If
more than one DTC is present, the DTCs will be
displayed in ascending order. If there are no DTCs,
the ignition key light and ceiling light will not blink
again after the Mode 1 indication.
Go to step 9.
Go to Mode 2 Test (see page 22-191).
9. Troubleshoot the DTC(s) in the order indicated
using the following charts.
If a faulty control unit is suspected, substitute it
with a known-good part and recheck for DTCs.
• If the DTC(s) is still present, go to the next step
listed for the DTC.
• If the DTC(s) is no longer present, replace the
original part.
(cont’d)
Ar e the f uses OK ?
Did the ignition key light and ceiling light indicate
mode 1?
Is ther e continuity?
Ar e ther e any DT Cs?
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Individual DTCs
Multiplex
DTC
Probable Cause
Multiple DTCs
Multiplex
DTCs
Probable Cause
22-190
Multiplex Control System
Troubleshooting (cont’d)
1
The multiplex control unit
cannot receive signals from
the gauge assembly.
1.
Faulty power or ground
to the gauge assembly
2.
Faulty gauge assembly
3.
Faulty under-dash fuse/
relay box
2
The multiplex control unit
cannot receive signals from
the ECM/PCM
1.
Faulty power or ground
to the ECM/PCM
2.
Faulty ECM/PCM
3.
Faulty under-dash fuse/
relay box
3
Internal failure of the
multiplex control unit
1.
Faulty under-dash fuse/
relay box
5
The gauge assembly cannot
receive signals from the ECM/
PCM
1.
Faulty power or ground
to the ECM/PCM
2.
Faulty gauge assembly
6
The ECM/PCM cannot receive
signals from the multiplex
control unit and the gauge
assembly
1.
Faulty power or ground
to the ECM/PCM
2.
Faulty gauge assembly
Before replacing a faulty ECM/PCM, make sure
it has the latest software revision. Update if
necessary before swapping or replacing.
1, 2 and 3
&
Short to ground on one of
the communication wires.
ECM DTC
P0600
Simultaneously
1.
Short to ground on the
YEL wire between the
ECM/PCM terminal E24
or E13 and the under-
dash fuse/relay box
terminal E10
2.
Short to ground on the
WHT/GRN wire
between the gauge
assembly terminal B13
or B11 and under-dash
fuse/relay box terminal
K10
1 and 6
Simultaneously
Open in the communication
wire
1.
Open in WHT/GRN
wire between the
under-dash fuse/relay
box terminal K10 and
the gauge assembly
terminal B13 or B11
2 and 5
Simultaneously
Open in the communication
wire
1.
Open in the YEL wire
between the under-
dash fuse/relay box
terminal E10 and ECM/
PCM terminal E10 and
ECM/PCM terminal E24
or E13
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Mode 2 Test
Switch
Lights blink when:
22-191
1. From mode 1, disconnect the special tool from the
multiplex inspection connector for 5 to 10 seconds,
and then reconnect it.
2. The ignition key light and ceiling light should come
on for 2 seconds, go out, then blink twice,
0.2 seconds each time. The system is now in Mode
2.
3. Operate the switches listed below: If the circuit is
OK, the ignition key light and ceiling light will blink
once. If the circuit is faulty, the lights will not blink.
•
•
Windshield washer
switch
Washer switch pulled
Windshield wiper
switch
Switch in the INT position
Driver’s door
switch
Driver’s door is opened
Passenger’s door
switch
Passenger’s door is
opened
Hatch latch switch
Hatch is opened
Parking brake
switch
Parking brake applied
Driver’s door lock
switch
Pushed to lock and
unlock
Driver’s door knob
switch
Knob in UNLOCK or
LOCK position
A/C switch
A/C switch ON and
blower switch ON
Headlight switch
Switched to the PARK
position
Brake pedal
position switch
Brake pedal pressed
Transmission
range switch
Shift P, R, D, D (A/T)
Upshift then downshift
(M/T)
4. If all inputs were confirmed, or multiple circuits
failed at the same time in Mode 2, go to the
Multiplex Sleep Mode Test. If a single switch fails
in Mode 2, troubleshoot its circuit.
(cont’d)
3
T ip: Oper ating the switches most closely r elated
to the pr oblem you ar e diagnosing is a quick way
of testing the cir cuits integr ity.
05/06/27 18:06:12 61S6M040_220_0192
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