Multiplex Integrated Control System Description
Multiplex Integrated Control System Description
Body Controller Area Network (B-CAN) and Fast Controller Area Network (F-CAN)
The body controller area network (B-CAN) and the fast controller area network (F-CAN) share information between multiple electronic control units (ECUs). B-CAN communication moves at a slower speed (33.33 kbps) for convenience related items and for other functions. F-CAN information moves at a faster speed (500 kbps) for "real time" functions such as fuel and emissions data. To allow both systems to share information, the gauge control module translates and relays the information from B-CAN to F-CAN and from F-CAN to B-CAN. This is called the Gate Way Function.
- The single wire method is used between the units not requiring the communication to move at a fast speed.
- Using a single wire method reduces the number of the wires used on the body controller area network.
Gateway Function
The gauge control module acts as a gateway to allow both systems to share information. The gauge control module translates and relays information from B-CAN to F-CAN and from F-CAN to B-CAN.
Network "Loss of Communication" Error Checking Function
The ECUs on the CAN circuit send messages to each other. If there are any communication malfunctions on the network, the multi-information display (MID) on the gauge control module can indicate the error messages by entering the gauge self-diagnostic function Testing and Inspection.
Self-Diagnostic Function
By connecting the HDS to the data link connector (DLC), the HDS can retrieve the diagnostic results from the MICU via a diagnostic line called the K-LINE. The K-LINE is a separate communication line from the CAN line, but it is connected to most of the CAN related ECUs. The MICU is a gateway between the HDS and B-CAN related ECUs, and sends B-CAN diagnostic results to the HDS. When performing a function test with the HDS, the HDS sends an output signal through the K-LINE to the MICU. The MICU either relays the request to another ECU, or commands the function itself.
Wake-Up and Sleep Function
The multiplex integrated control system has "wake-up" and "sleep" functions to decrease parasitic draw on the battery when the ignition switch is turned to LOCK (0).
- In the sleep mode, the MICU 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 to LOCK (0) with all the doors and the tailgate closed, and the driver's door is opened, then closed, there is a delay about 40 seconds before the control unit goes from the wake-up mode to the sleep mode.
- The sleep mode will not function if any door and tailgate are opened or if a key is in the ignition.
NOTE: Sleep and Wake-Up Mode Test Multiplex Integrated Control System Sleep and Wake-Up Mode Test.
Fail-Safe Function
To prevent improper operation, the MICU 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 a CPU malfunction, and a software fail-safe function that ignores the signal from a malfunctioning control unit, which allows the system to operate normally.
Hardware Fail-Safe Control
Fail-safe function
When a CPU problem or an 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 compulsorily fixed to a pre-programmed value.
Power Supply Voltage Monitoring Function
The MICU monitors the power supply voltage (back-up voltage). If the voltage drops below 10 V, the MICU does not store DTCs.
Entry Lights Control System (Ceiling Light, Map Lights, Ignition Key Light)*
The MICU controls the interior lights ON/OFF based on inputs from each switch.
Lighting System (Headlights, Parking Lights, Side Marker Lights, Fog Lights, License Plate Lights, and Taillights)*
The MICU contains the relay circuits of the headlight high/low beams and taillights, and controls the lighting system ON/OFF based on inputs from the combination light switch.
Daytime Running Lights
The MICU controls the exterior lights and daytime running lights based on inputs from each switch.
Automatic Lighting System
The MICU controls the automatic lighting system based on inputs from each switch.
Turn Signal/Hazard Warning Lights
The MICU controls the turn signal/hazard warning lights based on inputs from the turn signal and hazard warning switches.
Power Door Locks (Vehicle Speed Sensor)*
The MICU controls the door lock actuators based on inputs from each switch.
Power Door Locks (Normal LOCK/UNLOCK Operation)*
The MICU controls the door lock actuators based on inputs from each switch.
Door Lock Response Operation*
The MICU controls the door lock actuators based on B-CAN door lock signals.
Power Window Key-off Operation
The MICU controls the power windows key-off operation based on inputs from each switch.
Keyless Entry System*
The MICU controls the door lock actuators based on inputs from each switch.
Keyless PANIC
The MICU controls the keyless PANIC operation based on keyless signals sent by B-CAN data.
Security Alarm System*
The MICU controls the lighting system and horn based on inputs from each switch.
Key Interlock
The MICU controls the key interlock solenoid based on IG1, the transmission range switch, and the park-pin switch signals.
Answer Back Response Operation *
The MICU controls the lighting system and keyless buzzer based on keyless signals sent by B-CAN signals.
Windshield Wiper/Washer
The MICU controls the windshield wiper motor and the washer motor based on IG1, the wiper/washer switch, and the windshield wiper motor.
Rear Window Wiper/Washer
The MICU controls the rear window wiper motor and the washer motor based on IG1, the wiper/washer switch, and the rear window wiper motor.
Collision Detection Signal (CDS)
The MICU controls the door lock actuators based on IG1 and the SRS (CDS) inputs.
HDS Inputs and Function Tests
Certain inputs happen so quickly that the Data List on the HDS cannot update fast enough. Hold the switch that is being tested while monitoring the Data List. This should give the HDS time to update the signal on the Data List.
Because the HDS software is updated to support the release for newer vehicles, it is not uncommon to see system function tests that are not supported.
Make sure that the most current HDS software is loaded.
Input:
Function Test:
