Eaton Fuller Hybrid Transmission Fault Code 53 – DC/DC Converter

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. The DC/DC Converter is connected to the high-voltage Power Electronics Carrier (PEC), which provides 340 volts DC. The voltage is stepped down to 12-volts DC and used to maintain the 12-volt system during engine off PTO operation. The DC/DC maintains a steady 12.6 volts output and increases the amperage with vehicle demand up to 1.5 kw or 120 amps.

Fault Code 53 – DC/DC Converter 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.

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

Conditions to Set Fault Code Active

  • FMI 12 and FMI 14 set for the following reasons:
    • Vehicle voltage drop is greater than 0.7 volts at the start of ePTO mode.
    • Vehicle battery voltage is equal to or less than 11.3 volts.
    •  If there is no converter to battery cable fault, power drop across the converter is less than 900 watts (FMI 12), or power drop across the converter is greater than 1500 watts (FMI 14).

Fallback When Fault Code 53 is set the following conditions occur:
• Amber “Check Hybrid” light illuminates.
• Fault is stored in Hybrid Control Module (HCM) memory.
• HCM requires the engine to power the PTO and maintain the 12-volt system.

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 12
    • DC/DC Converter
  • FMI 14
    • Vehicle load is above the maximum 1.5 kw output of the converter.

Fault Code 53 – DC/DC Converter Test

Component Identification MY09 System:

Eaton Fuller transmission component identification

DC/DC Converter

1. Top: DC negative (-); Bottom: DC positive (+)
2. 12-volt DC negative (-)
3. 12-volt DC positive (+)

4. OEM connection
5. Coolant Ports

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.

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