Eaton Fuller Hybrid Transmission Fault Code 49 – J1939 Engine 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, 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 and International truck. J1939 is a high-speed twisted pair 250K data link with one 120 ohm resistor at each end of the link. The Hybrid Control Module (HCM) is connected to the J1939 data link at the 38-Way Connector. This link transmits information to the HCM and communicates with other modules on the network such as the Electronic Control Unit (ECU).

Fault Code 49 – J1939 Engine 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.
  • J1939 data link communication 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 fails to receive Engine ECU data (like engine torque) for 30 consecutive messages or greater, while still communicating with other modules on J1939.

Fallback When Fault Code 49 is set the following conditions occur:

  • Amber “Check Hybrid” light illuminates.
  • Fault is stored in Hybrid Control Module (HCM) memory.
  • Operation mode changes to “AutoShift Only” mode.
  • Electric Motor/Generator Assist and Regeneration are disabled; however, high-voltage relays remain powered.
  • 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 9
    • J1939 Data Link from Engine ECU
    • ECU

Fault Code 49 – J1939 Engine Message (HCM) Test

Component Identification:

HCM - Vehicle Interface Connector

Harness Front View
(HCM – Vehicle Interface Connector)

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

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

Eaton Fuller Transmission ECM HCM connector

STEP 1. Check for Active and Inactive fault code status.

  1.  Retrieve Active fault codes and FMIs with ServiceRanger using the 9-Way Diagnostic Connector.
    • If Fault Code 49 is Active, concern is either with the Engine ECU or the Data Link from Engine ECU to J1939 Data Link Backbone. Refer to OEM for repair procedure.
    • If Fault Code 49 is Inactive, test is complete.

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