Eaton Fuller Hybrid Transmission Fault Code 103 High Voltage Battery 1 Control Unit Communication

Fault code for Eaton Hybrid Drive Systems models (MY08) EH-8E306A-U, EH-8E306A-UPG, EH-8E306A-UP, EH-8E306A-CD, EH-8E306A-T, EH-6E606B-CD, (MY09) EH-8E406A-U/P, EH-8E406A-UP, EH-8E406A-UPG, EH-8E406A-CD, EH-8E406A-CDG, EH-8E406A-CDR, EH-8E406A-T, EH-6E706B-CD, EH-6E706B-P and EH-6E706B-UPG. Read below to learn how to test, clear and fix fault code errors for your Freightliner, Mack, Peterbilt, Kenworth, Volvo, International, and heavy-duty truck and equipment. The high-voltage batteries each contain a cell controller that communicates over a twisted pair data link to the Battery Control Unit (BCU). The Battery Control Unit located in the Relay Box communicates with each battery to determine temperature, State Of Charge, and voltage. This information is then sent to the Inverter.

Fault Code 103 High Voltage Battery 1 Control Unit Communication Detection

The following preconditions must be met before the system detects the fault:

  • Inverter ignition voltage is greater than 7 volts and less than 16 volts.
  • Battery Control Unit ignition voltage is greater than 7 volts and less than 16 volts.

Note: When troubleshooting an Inactive code refer to the Product Diagnostic Mode (PDM)

Conditions to Set Fault Code Active

  • FMI 22 is set when the BCU fails to communicate over the CAN data link for 30 ms.
  • FMI 23 is set when the BCU fails to receive HCM data over the CAN data link for 2.5 seconds or greater after communication is established.
  • FMI 24 is set when the BCU fails to receive Inverter data over the CAN data link for 2.5 seconds or greater after communication is established.
  • FMI 25 is set when the BCU detects an error on initial check.
  • FMI 26 is set when the BCU fails to transmit anything over the data link for 2 seconds.

Fallback When Fault Code 103 is set the following conditions occur:

  • Amber “Check Hybrid” light illuminates.
  • Fault is stored in Hybrid Control Module (HCM) memory.
  • Inverter shuts high-voltage system off.
  • HCM continues to control the hybrid vehicle in a diesel-only mode.
  • Transmission defaults start gear to 1st.

Conditions to Set Fault Code Inactive

Only Inactive faults can be cleared from the Transmission Electronic Control Unit (TECU) or HCM history using ServiceRanger. The TECU automatically clears the faults from history after 200 hours and the HCM automatically clears the faults from history after the fault has been Inactive for 200 hours.

This fault code can be caused by any of the following:

  • FMI 26
    • PEC
  • FMI 2, 22, 25
    • PEC
    • CAN Data Link between PEC and Inverter
  • FMI 23
    • CAN Data Link between PEC and HCM
    • Relay Box
    • PEC
  • FMI 24
    • PEC
    • Inverter
    • Relay Box
    • CAN Data Link between PEC and Inverter

Fault Code 103 High Voltage Battery 1 Control Unit Communication Test

Component Identification:

HCM - Hybrid System Interface Connector

Harness Front View
(HCM – Hybrid System Interface Connector)

56-Way Mating Connector View (Inverter - Low Voltage Connector)

56-Way Mating Connector View
(Inverter – Low Voltage Connector)

19 - Way Mating Connector View (PEC - Low Voltage Connector)

19 – Way Mating Connector View
(PEC – Low Voltage Connector)

NOTE: Refer to the Eaton Hybrid Component and Connector Location for Connector Locations in MY08 Systems

HCM Inverter PEC connectors on Eaton Fuller transmission

Component Identification:

HCM - Hybrid System Interface Connector

Harness Front View
(HCM – Hybrid System Interface Connector)

Duetsch 40-way mating connector view

Duetsch 40-Way Mating Connector View
(Inverter Low Voltage Connector)

19 - Way Mating Connector View (PEC - Low Voltage Connector)

19 – Way Mating Connector View
(PEC – Low Voltage Connector)

NOTE: Refer to the Eaton Hybrid Component and Connector Location for Connector Locations in MY09 Systems.

HCM Inverter PEC Connector location

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