System Overview

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Power is supplied by the vehicle power distribution modules (PDMs) to electronic control units (ECUs). The ECUs coordinate power to outputs such as lighting, displays, gauges, and indicators and control power distribution by monitoring inputs such as sensors and switches. 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

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.

Note:  Some non-critical faults may be suppressed and will not appear during an instrumentation control unit (ICU) self-check.

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:

  1. Use the buttons on the left-hand steering wheel to navigate to the wrench icon and press OK.
  2. ECUs with active faults will have an exclamation point next to them. Use the down arrow to select the affected ECU from the list, then press OK
    Refer to thee ECU acronyms list for the full names of acronyms on the ICU screen. See Table..

    Fig. 2, Electronic Control Unit (ECU) List in the ICUC

  3. 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

  4. 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

      To troubleshoot and resolve fault codes, take the vehicle to an authorized Freightliner service center for diagnostics.

    Note:
    Parent topic: Electrical System
    Document Number: 0000111708
    Manual Publication Date: 2024-10-09
    Topic Publication Date: 2024-05-07