Eaton Fuller Hybrid Transmission Fault Code 70 – Engine Failed to Respond (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, International, and heavy-duty truck and equipment. The Hybrid Control Module (HCM) communicates with the Engine Electronic Control Unit (ECU) over the J1939 data link during normal operation to control the engine torque and speed for transmission shifting.

Fault Code 70 – Engine Failed to Respond (HCM) Detection

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

  • Hybrid Control Module (HCM) ignition voltage is greater than 7 volts and less than 16 volts.
  • J1939 Communication Link Fault (HCM) is Inactive.
  • J1939 Engine Message Fault (HCM) is Inactive.

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

Conditions to Set Fault Code Active

  • FMI 7 is set when the HCM commanded engine torque is less than 80% Max Engine Torque.
  • HCM commanded engine torque is greater than 100 ft. lbs, and the difference between commanded engine torque and engine torque feedback is greater than 80 lb-ft for more than 1 second.
  • Engine speed or torque maps are received with an error.

Fallback When Fault Code 70 is set the following conditions occur:

  • Amber “Check Hybrid” light illuminates.
  • Fault is stored in Hybrid Control Module (HCM) memory.
  • If the fault is set while driving, the vehicle may experience shifting concerns.

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 7
    • Engine
    • Fuel system
    • Exhaust back pressure
    • Turbo charger
    • Air Intake/filter restriction
    • Unreported engine loads
    • Incorrect engine configuration settings for transmission assembly

Fault Code 70 – Engine Failed to Respond (HCM) Test

Component Identification MY09 System:

Hybrid control module

1. Hybrid Control Module (HCM)
2. Nut (3)
3. 38-Way System Connector Plug-in
4. 38-Way Vehicle Connector Plug-in
5. Mounting Plate

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

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