System Overview
Your Western Star has a multiplex electrical system. By transmitting multiple electronic messages through the same wire, a multiplex system reduces the number of interconnected wires, allows for more precise control of the electrical system, and makes it easer and quicker to diagnose electrical faults and add optional equipment.
In addition, the wiring harnesses are developed for the maximum number of options, meaning that space for additional wires is available within the wiring harness regardless of the number of optional features on the vehicle. This design provides a cleaner main harness and is meant to eliminate the need for wiring overlays
Traditional power distribution devices are replaced with electronic control modules (ECUs). These coordinate power to outputs such as lighting, displays, gauges, and indicators and control power distribution by monitoring inputs such as sensors and switches. Power is supplied by the vehicle power distribution module (VPDM).
The ECUs also continuously monitor the status of all input devices and transmit messages over multiple control area networks (CANs), reducing the number of sensors required for operation.
The Instrumentation Control Unit (ICU) and Fault Codes
Note: Some non-critical faults may be suppressed and will not appear during an instrumentation control unit (ICU) self-check.
The majority of electrical and electronic issues on the vehicle will have an associated fault code, which will be displayed on the ICU.
If the ICU receives active fault codes during the ICU self-check, it displays them one after the other until the parking brake is released or the ignition is turned off. Once the parking brake is completely released, the ICU displays alerts until acknowledged. See Fig.. If there are no active faults, the ICU displays the home screen after the self-check completes.
Fig. 1, ICUC Active Faults Alert Screen
When there is an active vehicle fault code, a popup will appear on the ICU message screen.
To access fault codes in the ICU:
- Use the buttons on the left-hand steering wheel to navigate to the wrench icon and press OK.
- ECUs with active faults will have an exclamation point
next to them. See Fig.. Use
the down arrow to select the affected ECU from the list, then press
OK
Fig. 2, Electronic Control Unit (ECU) List in the ICUC
- Locate the code to troubleshoot from the list of active
fault codes, then press OK to access the information screen. See Fig..
Fig. 3, Information Screen for an Active Fault Code
- Press OK again to access additional information. See Fig..
Fig. 4, Additional Information for the Fault
Table 1, ICU Electronic Control Unit Acronyms
ICU Electronic Control Unit Acronyms
ABS
Antilock Brake System
ICU
Instrumentation Control Unit
ACM
Aftertreatment Control Module
MCM
Motor Control Module
CGW
Central Gateway
RDF
Radar Front End
CPC
Common Powertrain Controller
SAS
Steering Angle Sensor
DCMD
Door Control Module, Driver
SSAM
Single Signal Detect and Actuation Module
DCMP
Door Control Module, Passenger
TCM
Transmission Control Module
HVCF
Heating/Ventilation/AC Front (HVAC)
TPMS
Tire Pressure Monitoring System
HVCP
Heating/Ventilation/AC, Auxiliary (HVAC)
VRDU
Video Radar Decision Unit
Table 1, ICU Electronic Control Unit Acronyms