Eaton Fuller Hybrid Transmission Fault Code 115 – Inverter Temperature

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 Inverter Temperature Sensor is a thermistor located inside the Inverter that changes in value based on the temperature. The Inverter supplies a 5-volt reference voltage to the sensor and measures the volt drop in the circuit.

When the Inverter temperature is warm the sensor resistance is low and the Inverter detects a low-voltage (0.1 volts equals 260 °F [127 °C]). When the Motor/Generator is cold the sensor resistance is high and the Inverter detects a high-voltage (4.0 volts equal -68 °F [-56 °C]).

Fault Code 115 – Inverter Temperature Detection

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

  • The Inverter 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 2 is set whenever DC/DC voltage feedback signal reads greater than 15 volts or less than 10 volts and ePTO mode is engaged.
  • FMI 4 is set if the voltage feedback is less than 15 volts and greater than 10 volts and the difference between the voltage feedback and the vehicle battery voltage is greater than 0.5 volts for 1 second or more.

Fallback When Fault Code 115 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 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 0
    • Inverter
    • Liquid cooling system (low coolant, no coolant flow, Coolant Pump, Radiator, Radiator Fan, Reservoir)

Fault Code 115 – Inverter Temperature Test

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