Eaton Fuller Hybrid Transmission Fault Code 90 – CAN BCU 2 Message (HCM)

Fault code for Eaton Hybrid Drive Systems models (MY08) EH-8E306A-U, EH-8E306A-UPG, EH-8E306A-UP, EH-8E306A-CD, EH-8E306A-T and EH-6E606B-CD. 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 Hybrid Control Module (HCM) communicate with the Inverter communicates with the Battery Control Unit (BCU) located in the Power Electronics Carrier (PEC) and the HCM on the Controller Area Network (CAN) high-speed proprietary data link. The data link is a two wire twisted pair with two 120 ohm resistors located in the link.

Fault Code 90 – CAN BCU 2 Message (HCM) Detection

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

  • HCM ignition voltage is greater than 7 volts and less than 16 volts.
  • HCM CAN data link fault is Inactive.

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

Conditions to Set Fault Code Active

  • FMI 9 is set when the HCM has not received an BCU 2 message for 30 consecutive message cycles.

Fallback When Fault Code 90 is set the following conditions occur:

  • Amber “Check Hybrid” light illuminates.
  • Fault is stored in Hybrid Control Module (HCM) memory.
  • Electric Motor/Generator Assist and Regeneration are disabled; however, high-voltage relays remain powered.
  • HCM continues to control the hybrid vehicle in a diesel-only mode.
  • Transmission defaults start gear to

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:

  • FMI9
    • Inverter
    • PEC
    • CAN Data Link from PEC to Inverter

Fault Code 90 – CAN BCU 2 Message (HCM) Test

Component Identification:

HCM - Hybrid System Interface Connector

Harness Front View
(HCM – Hybrid System Interface Connector)

Delphi 56-Way Mating Connector View for Eaton Fuller transmission

Delphi 56-Way Mating Connector View

PEC - Low Voltage Connector

PEC – Low Voltage Connector

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

Eaton Fuller transmission HCM inverter PEC Connectors

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