Acura TSX / Honda Accord CL. Manual - part 143

Fig. 2: Locating Multiplex Integrated Control System Components (2 Of 2) 

SYSTEM DESCRIPTIONS 

BODY CONTROLLER AREA NETWORK (B-CAN) & FAST CONTROLLER AREA NETWORK (F-
CAN): 

Fast Controller Area Network (F-CAN) and Body Controller Area Network (B-CAN) share information 
between multiple Electronic Control Units (ECUs). B-CAN communication moves at a slower speed for 
convenience related items, and for other functions. F-Can information moves at a faster speed for "real time" 
functions such as fuel and emissions data. To allow both systems to share information, the Gauge Control 
Module translates information from B-CAN to F-CAN and from F-CAN to B-CAN. 

The ECUs on the B-CAN and F-CAN transmit and receive information in the form of structured messages that 
may be received by several different ECUs on the network at one time. These message are transmitted and 
received across a communication circuit that consists of a single wire that is shared by all the ECUs on the 
circuit. Since messages on the F-CAN network are typically of higher importance, a second wire is used for 
communication circuit integrity monitoring. A backup circuit is also added to the headlight and wiper circuits 

 

2004 Acura TSX 

2004 ACCESSORIES & EQUIPMENT Multiplex Integrated Control System - TSX

  

 

on the B-CAN network in the event of a network wire or ECU failure that would effect the operation of the 
system. 

Fig. 3: Network Schematic 

Messages are transmitted by an ECU (that monitors an input) over the communication circuit. ECUs that use 
the message (information related to that input) are the receivers. For example, the Combination Switch Control 
Unit monitors the wiper switch. When the wiper switch is placed in the low speed position, the Combination 
Switch Control Unit transmits that message on the communication circuit. The Relay Control Module receives 
the message and turns on the wipers by providing a ground for the relay.

 

2004 Acura TSX 

2004 ACCESSORIES & EQUIPMENT Multiplex Integrated Control System - TSX

  

 

Fig. 4: Combination Switch Control Unit Monitoring The Wiper Switch 

"CONNECTED" ECUS 

Several ECUs are connected to each of the two networks. The Gauge Control Module is part of both networks 
since it is the "Gateway" between them. Below is a list of ECUs and the network they are connected to. 

B-CAN ECUS 

z

Gauge Control Module  

z

Relay Control Module  

z

Multiplex Integrated Control Unit (MICU)  

z

Door Multiplex Control Unit  

z

Combination Switch Control Unit  

 

2004 Acura TSX 

2004 ACCESSORIES & EQUIPMENT Multiplex Integrated Control System - TSX

  

 

z

Climate Control Unit  

F-CAN ECUS 

z

Gauge Control Module  

z

ECM/PCM  

z

Navigation Control Unit  

z

VSA (Vehicle Stability Assist)  

Fig. 5: Network Schematic 

NETWORK "LOSS OF COMMUNICATION" ERROR CHECKING 

The B-CAN and F-CAN systems send messages to each other to check the integrity of the network 
communication circuit. They do this by sending a specific digital message out after an event. For example, 
turning the ignition switch to ON. After the switch to ON, all the ECUs on the communication circuit expect to 
receive a message from other specific units within a specified amount of time. If the message is not received, 
the ECU will transmit a DTC reporting that the control units did not communicate. 

EXAMPLE OF COMMUNICATION CIRCUIT TEST 

Normal Circuit 

1. Ignition switch turned ON.  

2. The door multiplex control unit transmits a door switch signal.  

3. The multiplex integrated control unit (MICU), relay control module and gauge control module receive the 

door lock switch signal.  

4. Communication circuit test is passed. 

 

2004 Acura TSX 

2004 ACCESSORIES & EQUIPMENT Multiplex Integrated Control System - TSX