MICU System Description

The MICU that is combined with the under-dash fuse/relay box is the one of the B-CAN network components. The MICU controls many systems related to the body controller area and security system. and also works as a gateway to the diagnose the other B-CAN connected ECUs with the HDS.
Refer to each system circuit diagram for details.

MICU Control Function Index


System Function 
Multiplex Control Sends the switch signal information to the MICU and output the information. The MICU controls the ECUs electric load and communication based upon the information received from the B-CAN. 
On-Board Diagnosis The MICU has a gateway function which sends the results of the MICU internal diagnosis and the B-CAN connected ECUs diagnosis to the HDS. 
Self-Diagnosis Test mode 1 diagnoses the communication line between the MICU and B-CAN connected unit. Test mode 2 checks the switch inputs connected to the MICU. 
Interior Light(s) The MICU controls the interior lights ON, OFF and dimming based upon the information of the related switches and/or the B-CAN related information. 
Sleep Function The MICU has a sleep function, which it enters during power down mode. 


The MICU also controls the function of these circuits:

*: With sunroof 


Hardware Fail-safe Control


Fail-safe Function


When a CPU problem or a abnormal power supply voltage is detected, the MICU moves to the hardware fail-safe mode, and each system output load is set to the pre-programmed fail-safe value.

Software Fail-safe Control


When any of the data from the B-CAN circuit cannot be received within a specified time, or an unusual combination of the data is recognized, the MICU moves to the software fail-safe mode. The data that cannot be received is forced to pre-programmed value.

Power Supply Voltage Monitoring Function


The MICU monitors the power supply voltage (back-up voltage). If the voltage goes below 10 V, the MICU sends a MICU message and will not store DTCs.

 Input Output 
MICU Battery voltage MICU*
*: MICU internal circuit 


Gauge Control Module


MICU communicates with the gauge control module by B-CAN.

 Input Output 
B-CAN Vehicle speed pulse Driver's door switch 
 Engine RPM Front passenger's door switch 
  Left rear door switch 
  Right rear door switch 
  Trunk lid latch switch 
  Lighting switch 
  Headlight switch 
  Dimmer switch (high beam) 
  Ignition key switch 


Entry Lights Control System


The MICU controls the ceiling light ON/OFF and dimming based upon the input signals from each switch.

 Input Output 
MICU IG1 power supply Interior light 
 Ignition key switch  
 Driver's door switch  
 Front passenger's door switch  
 Left rear door switch  
 Right rear door switch  
 Driver's door lock knob switch (LOCK)  
B-CAN Keyless LOCK signal  


Lighting System (Headlights, Position Lights, Front fog light, Rear fog light and Taillights)


The MICU contains the relay circuits of the headlight high/low beam and taillights, and controls the lighting system ON/OFF based upon the input signals from the combination light switch.

 Input Output 
MICU Headlight OFF switch Headlight (low beam) 
 Headlight ON switch Headlight (high beam) 
 Dimmer switch Position lights and taillights 
 Combination light switch (position lights and taillight) Front fog light 
 Passing switch Rear fog light 
 Front fog light switch  
 Rear fog light switch  

Turn Signal/Hazard Flasher


The MICU controls the turn signal/hazard flasher based upon the input signals from the turn signal and hazard warning switch.

 Input Output 
MICU IG1 power supply Turn signal lights (left/right) 
 Turn signal switch (left/right)  
 Hazard warning switch  


Power Door Locks (Vehicle Speed Sense)


The MICU controls the door lock actuators based upon the B-CAN signals and the input signals.

 Input Output 
MICU IG1 power supply Door lock (LOCK) 
 Driver's door switch  
 Front passenger's door switch  
 Left rear door switch  
 Right rear door switch  
 Driver's door lock knob switch (UNLOCK)  
 Front passenger's door lock knob switch (UNLOCK)  
 Left rear door lock knob switch (UNLOCK)  
 Right rear door lock knob switch (UNLOCK)  
 Transmission range switch (P position)  
B-CAN Vehicle speed pulse  
 Engine RPM  


Power Door Locks (Normally LOCK/UNLOCK operation)


The MICU controls the door lock actuators based upon the input signals of the each switch.

 Input Output 
MICU IG1 power supply Door lock actuators (LOCK/UNLOCK) 
 Ignition key switch  
 Driver's door switch  
 Front passenger's door switch  
 Left rear door switch  
 Right rear door switch  
 Driver's door lock switch (LOCK/UNLOCK)  
 Front passenger's door lock switch (LOCK/UNLOCK)  
 Driver's door key cylinder switch (UNLOCK)  
 Driver's door lock knob switch (LOCK)  


Door Lock Response Operation


The MICU controls the door lock actuators based upon the B-CAN signals.

 Input Output 
B-CAN Door lock signal Door lock actuator (LOCK/UNLOCK) 
  Driver's door lock actuator (UNLOCK) 


Power Window Key-off Operation


The MICU controls the power window key-off operation based upon the input signals.

 Input Output 
MICU IG1 power supply Power window key-off timer 
 Driver's door switch  
 Front passenger's door switch  

Keyless Entry System


The MICU controls the door lock actuators based upon the input signals of the each switch, and the B-CAN signals.

 Input Output 
MICU IG1 power supply Door lock actuator (LOCK/UNLOCK) 
 Ignition key switch Driver's door lock actuator (UNLOCK) 
 Driver's door switch  
 Front passenger's door switch  
 Left rear door switch  
 Right rear door switch  
 Driver's door lock knob switch (LOCK/UNLOCK)  
 Driver's door lock switch (LOCK/UNLOCK)  
 Front passenger's door lock switch (LOCK/UNLOCK)  
 Driver's door key cylinder switch (LOCK/UNLOCK)  
B-CAN Keyless LOCK signal  


Security Alarm System


The MICU controls the lighting system and horn based upon the input signals of the each switch and the B-CAN signals.

 Input Output 
MICU IG1 power supply Horn(s) 
 Ignition key switch Headlights (low beam) 
 Audio switch Position lights and taillights 
 Driver's door switch  
 Front passenger's door switch  
 Left rear door switch  
 Right rear door switch  
 Trunk lid latch switch  
 Driver's door lock knob switch (UNLOCK)  
 Front passenger's door lock knob switch (UNLOCK)  
 Left rear door lock knob switch (UNLOCK)  
 Right rear door lock knob switch (UNLOCK)  
 Driver's door key cylinder switch (UNLOCK)  
 Front passenger's door key cylinder switch (UNLOCK)  
 Trunk key cylinder switch (UNLOCK)*  
 Hood switch  
B-CAN Keyless LOCK signal  
Door lock signal  

*: With trunk key cylinder switch 


Key-in Reminder


The MICU controls the door lock actuators based upon the IG1 signal, the driver's door switch signal and the driver's door lock knob switch signal.

 Input Output 
MICU IG1 power supply Door lock actuator (LOCK/UNLOCK) 
 Driver's door switch Driver's door lock actuator 
 Driver's door lock knob switch  

Key interlock (A/T)


The MICU controls the key interlock solenoid based upon the IG1 signal, the transmission range switch signal and the park-pin switch signal.

 Input Output 
MICU Ignition switch ACC Key interlock solenoid 
 Transmission range switch (P position)  
 Park-pin switch  


Answer Back Response Operation


The MICU controls the lighting system and horn based upon the B-CAN signals.

 Input Output 
B-CAN Answer back signal (headlight low, horn, position lights) Horn(s) 
 Keyless door lock signal Headlights (low beam) 
  Position lights and taillights 


Wiper/Washer


The MICU controls the wiper motor and the washer motor based upon the IG1 signal and wiper switch signal.

 Input Output 
MICU IG1 power supply Wiper motor 
 Wiper switch (INT and LO) Windshield washer motor 
 Wiper switch (HI and LO)  
 Wiper switch (MIST)  
 Windshield washer switch  
 Wiper intermittent speed  


Collision Detection Signal (CDS)


The MICU controls the door lock actuators based upon the IG1 signal and B-CAN signal.

 Input Output 
MICU IG1 power supply Door lock (LOCK/UNLOCK) 
B-CAN SRS signal (front, rear and side)
Impact sensors 		 


Super Locking System


The MICU controls the super locking actuators based upon the input signals of each switch, and the B-CAN signals.

 Input Output 
MICU IG1 power supply Door lock actuator (LOCK/UNLOCK) 
 Ignition key switch Super locking actuator 
 Driver's door switch  
 Front passenger's door switch  
 Left rear door switch  
 Right rear door switch  
 Driver's door lock knob switch (LOCK/UNLOCK)  
 Front passenger's door lock knob switch (LOCK/UNLOCK)  
 Left rear door lock knob switch (LOCK/UNLOCK)  
 Right rear door lock knob switch (LOCK/UNLOCK)  
 Driver's door key cylinder switch (LOCK/UNLOCK)  
B-CAN Keyless LOCK signal  
 Door lock signal