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

STEP 1.Verify Inverter temperature.

  1. Review and follow the Warnings & Cautions.
  2.  Retrieve Active fault codes and FMIs with ServiceRanger using the 9-Way Diagnostic Connector.
    Danger: See High-Voltage Service Shutdown and Power-Up Procedures. Follow the procedures to avoid shock, burn or death from improperly handled high-voltage.
  3. Key on.
  4. Select the Data Monitor option and view PID 120 Inverter Temperature in the “Power Electronics” list.
  5. Observe PID 120 again after 20 minutes.
    • If PID 120 Inverter Temperature lowered from the first to second reading, go to Step 2.
    • If PID 120 Inverter Temperature remained constant, replace the Inverter, then go to Step 8.

STEP 2. Verify Hybrid System coolant level.

  1. Key off
  2. Observe the coolant level after the system has cooled to see if it is filled to the proper level:
    • If the coolant is within the recommended limits, go to Step 3.
    • If the coolant is below the recommended limits, refer to OEM for coolant type and fill procedure, then go to Step 8.

STEP 3. Verify integrity of Hybrid Cooling System components.

  1. Visually inspect the Hybrid Liquid Cooling System Radiator for debris or obstruction to airflow and inspect the coolant lines for sharp bends:
    • If the radiator is free of debris and the coolant lines are not kinked, go to Step 4.
    • If the radiator is full of debris, the airflow is obstructed or the coolant lines are kinked. Repair the concern, then go to Step 8.

STEP 4. Verify hybrid system Coolant Pump operation.

  1. Key on.
  2. Connect ServiceRanger to the 9-Way Connector in the cab.
  3. Select the Advanced Product Functions option and select the “Cooling Pump” option.
  4. Enable the Cooling Pump option:
    • If the Coolant Pump turns on, go to Step 5.
    • If the Coolant Pump fails to turn on, go to Step 6.

STEP 5. Verify Hybrid System Heat Exchanger Fan operation.

  1. Select the Advanced Product Functions option and select the “Heat Exchanger Fan” option.
  2. Enable the Heat Exchanger Fan option.
    • If the Heat Exchanger Fan turns on, the system needs to be purged of air to allow the coolant to flow. Bleed the air by using a coolant system pressurizing tool or a vacuum tool, then go to Step 8.
    • If the Heat Exchanger Fan fails to turn on, go to Step 7.

STEP 6. Verify voltage at Hybrid System Coolant Pump.

  1. Key on.
  2. Disconnect the Coolant Pump 2-Way Connector.
  3. Select the Advanced Product Functions option and select the “Cooling Pump” option.
  4. Enable the Cooling Pump option.
  5. Measure the voltage at the 2-Way Connector from Pin A to Pin B.
    • If voltage between Pins A and B is ±0.2 volts of battery voltage, refer to OEM for Coolant Pump concern.
    • If voltage between Pin A and Pin B is outside of range, refer to OEM for Cooing Pump Power Harness repair procedure.

STEP 7. Verify voltage at Hybrid System Heat Exchanger Fan.

  1. Key on.
  2. Disconnect the Heat Exchanger Fan 2-Way Connector.
  3. Select the Advanced Product Functions option and select the “Heat Exchanger Fan” option.
  4. Enable the Heat Exchanger Fan option.
  5. Measure the voltage at the 2-Way Connector from Pin A to Pin B:
    • If voltage between Pins A and B is ±0.2 volts of battery voltage, refer to OEM for Heat Exchanger Fan concern.
    • If voltage between Pin A and Pin B is outside of range, refer to OEM for Heat Exchanger Fan Power Harness repair procedure.

STEP 8. Verify repair.

  1. Key off.
  2. Reconnect all connectors and the negative battery cable.
  3.  Key on.
  4. Clear codes, see  Clear Inactive Faults.
  5. Drive the vehicle and attempt to reset the code.
  6. Check for codes, see View Active and Inactive Faults.
    • If no codes, test is complete.
    • If fault Code 115 appears, find error in testing, go to Step 1.
    • If a code other than 115 appears, see Fault Code Index List.

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