Eaton Fuller Hybrid Transmission Fault Code 108 – High Voltage Battery 1 Control Unit Power Supply

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 high-voltage batteries are 172 volts each connected in series to produce 340 volts DC. The Battery Control Unit located in the Relay Box receives 12-volts ignition power and ground from the Inverter.

Fault Code 108 – High Voltage Battery 1 Control Unit Power Supply 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.

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

Conditions to Set Fault Code Active

  • FMI 3 is set when the BCU detects the ignition voltage is greater than 16 volts for 1 second.
  • FMI 4 is set when the BCU detects the ignition voltage is less than 7 volts for 1 second.

Fallback When Fault Code 108 is set the following conditions occur:

  • Amber “Check Hybrid” light illuminates.
  • Fault is stored in Hybrid Control Module (HCM) memory.
  • Inverter shuts high-voltage system off.
  • 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 3
    • PEC (MY08 Systems)
    • Relay Box (MY09 Systems)
  • FMI 4
    • Relay Box
    • Low-voltage harness from Inverter to Power Electric Carrier (PEC)
    • HCM
    • Low-voltage harness from HCM to Inverter
    • Inverter

Fault Code 108 – High Voltage Battery 1 Control Unit Power Supply Test

Component Identification MY08 Systems:

HCM - Hybrid System Interface Connector

Harness Front View
(HCM – Hybrid System Interface Connector)

Inverter 56-Way Mating Connector View

Delphi 56-Way Mating Connector View
(Inverter – Low Voltage Connector)

PEC - Low Voltage Connector

19 – Way Mating Connector View
(PEC – Low Voltage Connector)

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

HCM Inverter PEC connector pins

Component Identification MY09 Systems:

HCM - Hybrid System Interface Connector

Harness Front View
(HCM – Hybrid System Interface Connector)

Duetsch 40-way mating connector view

Duetsch 40-Way Mating Connector View
(Inverter – Low Voltage Connector)

PEC - Low Voltage Connector

19 – Way Mating Connector View
(PEC – Low Voltage Connector)

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

STEP 1. Check for Active or Inactive fault code status.

  1. Review and follow the Warnings & Cautions.
  2.  Retrieve Active fault codes and FMIs with ServiceRanger using the 9-Way Diagnostic Connector or manually.
  3. Key off.
    Danger: See High-Voltage Service Shutdown and Power-Up Procedures. Follow the procedures to avoid shock, burn or death from improperly handled high-voltage.
  4. Which Faults are present?
    • If Fault Code 108 FMI 3 or 4 are listed with an Active Fault Code 114, go to Fault Code 114 -Inverter Power Supply.
    • If Fault Code 108 FMI 3 or 4 are listed with no Active Fault Code 114, go to Step 2.

STEP 2. Verify voltage at PEC connector.

  1. Disconnect the PEC 19-Way Connector.
  2. Connect a multimeter to the PEC 19-Way Connector Pin 6 and Pin 7.
  3. Place multimeter where it can be viewed, while standing next to the truck.
  4.  Key on.
  5. Observe multimeter voltage reading:
    • If voltage between Pin 6 and Pin 7 is 11–13 volts, replace the Power Electronics Carrier (PEC), then go to Step 4.
    • If voltage between Pin 15 and Pin 1 is less than 7 volts, go to Step 3.

STEP 3.(MY08) Verify continuity between PEC and Inverter connectors.

  1. Key off.
  2. Disconnect the Inverter 56-Way Connector.
  3. Measure resistance on the following:
    • Inverter 56-Way Connector Pin 16 to PEC 19-Way Connector Pin 6.
    • Inverter 56-Way Connector Pin 34 to PEC 19-Way Connector Pin 7.
      Note: Gently flex the Inverter 56-Way Connector Harness near the Connector while monitoring the voltage values.

      • If resistance from Pin 16 to Pin 6 is 0–0.3 ohms and resistance from Pin 34 to Pin 7 is 0–0.3 ohms, replace the Inverter, then go to Step 4.
      • If resistance is outside of range, replace the low-voltage harness from the PEC to the Inverter, then go to Step 4.

STEP 3.(MY09) Verify continuity between PEC and Inverter connectors.

  1. Key off.
  2. Disconnect the Inverter 40-Way Connector.
  3. Measure resistance on the Inverter 40-Way Connector Pin 14 to PEC 19-Way Connector Pin 6 and the Inverter 40-Way Connector Pin 15 to PEC 19-Way Connector Pin 7:
    • If resistance from Pin 14 to Pin 6 is 0–0.3 ohms and resistance from Pin 15 to Pin 7 is 0–0.3 ohms, replace the Inverter, then go to Step 4.
    • If resistance is outside of range, replace the low-voltage harness from the PEC to the Inverter, then go to Step 4.

STEP 4. 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 108 appears, find error in testing, go to Step 1.
    • If a code other than 108 appears, see Fault Code Index List.

Any transmission part you need we have it! Same day shipping available, worldwide.

NEED FREE SUPPORT FROM ONE OF OUR EXPERTS?

CALL NOW
EMAIL US