Multiplex Integrated Control System Troubleshooting - Test Mode 1

B-CAN System Diagnosis Test Mode 1
(Troubleshooting without the PGM Tester or the HDS)


1.Check the No. 9 (10A) fuse and No. 21 (7.5A) fuse in the under-dash fuse/relay box.

Are the fuses OK?


YES - Go to 2.


NO - Find and repair the cause of the blown fuse.n


2.Check self-diagnosis function Mode 1 for a diagnostic trouble code (DTC).

3.If there is a DTC, it will blink, pause, then repeat the DTC as long as the ignition switch ON (II).

Is there a repeating DTC?


YES - Count the blinks, then go to 4.


NO - Go to 5.

4.About 1 second after you go into self-diagnosis Mode 1, the ceiling light will indicate the DTC, and repeat it every 3 seconds. If there is more than one DTC, the system will indicate them in ascending order, beginning from the DTC with the lowest numerical value. Troubleshoot the DTCs as indicated below:

  • DTC 2, 3, 4 and 5 simultaneously: Check for an open in the BLU wire between multiplex integrated control unit D11 and relay module J7, BRN/RED wire between multiplex integrated control unit J4 and door multiplex control unit No. 16, LT BLU wire between multiplex integrated control unit X27 and combination switch control unit No.4, WHT wire between multiplex integrated control unit N28 and gauge B25. If the wire is OK, substitute a known-good under-dash fuse/relay box (multiplex integrated control unit), under-hood fuse/relay box, power window master switch, wiper/washer switch and gauge one at a time, in that order, and recheck for the DTCs after each substitution.
  • DTC 1 only go to MICU input test.
  • DTC 2 only (no other DTCs present): Go to the relay module input test. If all inputs are OK, substitute a known-good relay module and then a MICU, one at a time, and then check for DTCs. If a DTC recurs after a substitution, replace that unit.
  • DTC 3 only (no other DTCs present): Go to the door multiplex control unit input test. If all inputs are OK, substitute a known-good door multiplex control unit and then a MICU, one at a time, and then check for DTCs. If a DTC recurs after a substitution, replace that unit.
  • DTC 4 only (no other DTCs present): Go to the combination switch control unit input test. If all inputs are OK, substitute a known-good wiper/washer switch and then a MICU, one at a time, and then check for DTCs. If a DTC recurs after a substitution, replace that unit.
  • DTC 5 only (no other DTCs present): Go to the gauge control module input test. If all inputs are OK, substitute a known-good gauge control module and then a MICU, one at a time, and then check for DTCs. If a DTC recurs after a substitution, replace that unit.

DTC Cause 
1 The MICU cannot receive signals from the BUS communication line. 
2 The MICU cannot receive signals from the relay module communication line. 
3 The MICU cannot receive signals from the power window communication line. 
4 The MICU cannot receive signal from the combination switch communication line. 
5 The MICU cannot receive signals from the gauge control module. 


5.Switch the MICS to Mode 2.

6.Look in the following table for the switches most closely related to the problem then operate that switch. If the circuit is OK, the ceiling light should blink once. If the circuit is faulty, there will be no indication.
In the table below is a list of circuits that can be checked in Mode 2.


Unit: MICU
Item 
Driver's door switch 
Front passenger's door switch 
Left rear door switch 
Right rear door switch 
Trunk latch switch 
Front passenger's door lock knob switch (UNLOCK) 
Left rear door lock knob switch (UNLOCK) 
Right rear door lock knob switch (UNLOCK) 
Ignition key switch 
Audio-HVAC-display module security ground (disconnected) 
Driver's seat belt switch (unbuckled) 
Brake pedal position switch 


Unit: RELAY CONTROL MODULE
Item 
Windsheld wiper switch (motor park) 
Hood switch 
A/C pressure switch 



Unit: COMMBINATION SWITCH CONTROL UNIT
Item 
Turn signal switch (LEFT) 
Turn signal switch (RIGHT) 
Combination light switch 
Dimmer switch 
Passing switch 
Windsheld wiper switch 
Intermttent dwell time controller 
Windsheld washer switch 


Unit: POWER WINDOW MASTER SWITCH (DOOR MULTIPLEX CONTROL UNIT
Item 
Power window master switch (DRIVER'S MANUAL UP) 
Power window master switch (DRIVER'S MANUAL DOWN) 
Power window master switch (DRIVER'S AUTO UP) 
Power window master switch (DRIVER'S AUTO DOWN) 
Power window master switch (FRONT PASSENGER'S UP) 
Power window master switch (FRONT PASSENGER'S DOWN) 
Power window master switch (LEFT REAR UP) 
Power window master switch (LEFT REAR DOWN) 
Power window master switch (RIGHT REAR UP) 
Power window master switch (RIGHT REAR DOWN) 
Driver's door key cylinder switch (LOCK) 
Driver's door key cylinder switch (UNLOCK) 
Driver's door lock switch (LOCK) 
Driver's door lock switch (UNLOCK) 
Driver's door lock knob switch (LOCK) 
Driver's door lock knob switch (UNLOCK) 
Keyless receiver (LOCK) 
Keyless receiver (UNLOCK) 
Keyless receiver (TRUNK) 


Unit: GAUGE CONTROL MODULE
Item 
Parking brake switch 
Cruise Set/Resume/Cancel switch 
Transmission range switch 
Brake fluid level switch 


Does the ceiling light indicate proper switch operation?


YES - Go to function and input test for the system related to the failure.n


NO - Repair the open, short, or replace the faulty switch.n