Eaton Fuller Hybrid Transmission Fault Code 91 – APG Unit 1 CAN

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 Auxiliary Power Generator (APG) is a 5kW/5kVA DC/AC Inverter that is connected to the high voltage DC bus of the Eaton Hybrid electric vehicle system, and generates 60 Hz single-phase 120V AC power for utility applications. The Controller Area Network (CAN) is a high-speed twisted pair 500K proprietary data link that connects the HCM to the Electric Clutch Actuator (ECA), Battery Control Module, Inverter and APG. The link contains one 120 ohm resistor at each end. The link is used to transmit information specific to clutch position or power electronics operations.

Fault Code 91 – APG Unit 1 CAN 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.
  • HCM data link fault (FC60) 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 if communication from the APG unit is not received for 7.5 seconds and it is expected to be received based on the configuration settings: Vehicle Type = UPG and Number of APGs.

Fallback When Fault Code 91 is set the following conditions occur:

  • Amber “Check Hybrid” light illuminates.
  • Fault is stored in Hybrid Control Module (HCM) memory.
  • If the fault sets at command on the APG remains off.
  •  If the fault sets during operation the APG shuts off.

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
    • CAN Data Link near APG
    • APG

Fault Code 91 – APG Unit 1 CAN Test

Component Identification:

APG 8-way low-voltage harness connector

APG 8-Way Low-Voltage Harness Connector

Fuller transmission 9-way diagnostic connector

9-Way Diagnostic Connector

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

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