Eaton Fuller Hybrid Transmission Fault Code 116 – High Voltage Relays -(MY08 Systems)
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. 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 Relays are located inside the Power Electronics Carrier (PEC) in the Relay Box unit. There is 1 precharge relay on the positive side, an additional relay on the positive, and 1 on the negative for a total of 3. These relays are normally open when the system is off. The relays are controlled through the Inverter.
Fault Code 116 – High Voltage Relays Detection
The following preconditions must be met before the system detects the fault:
- 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 10 is set when the Inverter detects the input voltage measured at the capacitor is less than 210 volts within 3 seconds after the sub-relay closed in the Relay Box.
- FMI 14 is set when only the negative relay in the Relay Box is on and capacitor voltage decreases less than 10 volts/5 seconds when initial capacitor voltage was greater than 200 volts and motor speed less than 500 min-1, or there is a detect error in the initial check.
Fallback When Fault Code 116 is set the following conditions occur:
- Amber “Check Hybrid” light blinks for FMI 10 and remains solid for FMI 14.
- Fault is stored in 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 10
- PEC
- APG
- Inverter
- DC high-voltage cable
- DC cable interlock loops
- Inertia Switch
- Service Switch
- FMI 14
- Inverter
- PEC
Fault Code 116 – High Voltage Relays Test
Component Identification MY08 Systems:

56-Way Mating Connector View

High Voltage DC Connector View Yazaki Connector

Mating Connector View Deutsch 19 – Way
NOTE: Refer to the Eaton Hybrid Component and Connector Location for Connector Locations in MY08 Systems

Warnings & Cautions
Danger: Danger indicates you will be severely injured or killed if do not follow the indicated procedure.
Warning: Warning indicates an immediate hazard, which could result in severe personal injury if you do not follow the indicated procedure.
Caution: Caution indicates vehicle or property damage could occur if you do not follow the indicated procedure.
Note: Note indicates additional detail that will aid in the diagnosis or repair of a component/system.
Follow the specified procedures in the indicated order to avoid personal injury:
1. If the high-voltage cones are around the vehicle and the lockout is installed on the PEC, the only person that should be allowed to start the vehicle is the person who signed the lockout tag.
2. Before working on a vehicle or leaving the cab while the engine is running, you should place the shift lever in “N” set the parking brake, and block the wheels.
3. For safety reasons, always engage the service brakes prior to selecting gear positions from “N.”
4. Before starting a vehicle always be seated in the driver’s seat, select “N” on the shift control, and set the parking brakes.
5. In vehicles with ePTO, the engine and/or
Motor/Generator can start in ePTO mode. Never perform any maintenance or work on vehicle, while in this mode.
6. 12-Volt Battery positive (+) and negative (-) must be disconnected prior to any welding on any Hybrid equipped vehicle.
Caution: Follow the specified procedures in the indicated order to avoid equipment malfunction or damage.
Caution: Do not release the parking brake or attempt to select a gear until the air pressure is at the correct level.
Caution: To avoid damage to the transmission during towing place the shift lever in “N” and lift the drive wheels off the ground or disconnect the driveline.
High-Voltage Warnings & Cautions
- Use CO2 or Dry Chemical Fire Extinguishers.
- The high-voltage wiring is covered in orange insulation or convoluted tubing and marked with warning labels at the connectors.
- All Eaton® Hybrid Diesel/Electric vehicles will be marked ‘Hybrid’ on the outside of the vehicle, along with the shift label on the dash.
- Refer to OEM for specific location of chassis mounted hybrid components.
- Do NOT cut into the orange high-voltage cables.
- Do NOT cut into or open the PEC.
- Do NOT cut into or open the DC/DC Converter.
- Do NOT cut into or open the Inverter.
A buffer zone must be set up and high-voltage insulated rubber gloves (class 0 with leather protectors) are required prior to working on high-voltage. Failure to follow these instructions may result in severe personal injury or death.
The rubber-insulated gloves that must be worn while working on the high-voltage system are class 0 with leather protectors. The rubber gloves should be tested before EVERY use following the rubber insulation gloves testing procedure found in “Diagnostic Tools/Service Publications” on page 6. Failure to follow these instructions may result in severe personal injury or death.
Before inspecting or working on any high-voltage cables or components the “High-Voltage Service Shutdown and Power-Up Procedure” on page 4 should be followed. Failure to follow these instructions may result in severe personal injury or death.
The Lockout and Tagout devices should only be removed by the technician that placed the Lockout and Tagout devices on the vehicle. Failure to follow these instructions may result in severe personal injury or death.
High-voltage rubber insulated gloves (class 0 with leather protectors) must be worn when working on any
high-voltage cables. The “High-Voltage Service Shutdown and Power-Up Procedure” on page 4 must be followed prior to removing any high-voltage cables. Failure to follow these instructions may result in severe personal injury or death.
High-voltage cables and wiring are orange and contain a warning label at the connectors. High-voltage components are marked with a label. High-voltage rubber insulated gloves (class 0 with leather protectors) must be used when working on any of these components. Failure to follow these instructions may result in severe personal injury or death.
High-Voltage Service Shutdown Procedures
1. Follow “High-Voltage Work Area” procedure.
2. Locate the red PEC Service Switch on the front of the PEC and push switch off.
3. Remove the Service Switch Cover and install the Lockout Bracket (J48506).
4. Fasten tag to the Lockout Bracket.
5. Ensure the PEC Service Switch can not move from the off position.
6. Allow the system to set for a minimum of 5 minutes to discharge high voltage.
7. Connect ServiceRanger and view the Data Monitor PID 116 called “High-Voltage Battery Potential.” Use SPN 520323 for J1939 connection “Battery Voltage RB” (Relay Box).
8. The voltage should be 30 volts or less. If the voltage is above 30 volts, do not work on the vehicle and contact Eaton® at 1-800-826-HELP (4357).
9. Turn ignition key off and proceed to repair or troubleshooting step.
Note: The voltage drops to zero when the key is off.
High-Voltage Service Power-Up Procedure
1. Install all high-voltage connectors into their locked positions.
2. If you are the person working on the vehicle, remove the Lockout Bracket and tag.
3. Reinstall the Lockout Bracket over the Service Switch.
4. Pull the Service Switch out and let vehicle set for 2 minutes.
5. Start vehicle when appropriate.
Eaton Hybrid Component and Connector Location

Eaton Hybrid Component and Connector Location MY09 Systems

STEP 1. Verify FMIs present.
- Review and follow the Warnings & Cautions.
- 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. - Which FMIs are present
- If Fault Code 116 FMI 14 is listed, go to Step 9.
- If Fault Code 116 FMI 10 is listed, go to Step 2.
- If no Fault Codes are listed, The Service Switch was pushed in. Go to Step 10.
STEP 2. Verify Data Monitor parameters.
- Key on.
- Connect ServiceRanger to the 9-Way Diagnostic Connector in the cab.
- Select the “Data Monitor” option.
- View the Battery Pack Voltage (BCU1) PID 118 in the high- voltage Battery list:
- If the Battery Pack Voltage (BCU1) PID 118 is greater than 200 volts, go to Step 3.
- If the Battery Pack Voltage (BCU1) PID 118 is less than 200 volts, replace the Power Electronics Carrier (PEC), then go to Step 10.
STEP 3. Verify continuity of Inverter connector circuits.
- Key off.
- If the vehicle is not equipped with a DC/DC Converter or APG, skip this step.
- Using ASTM Class 0 electrical insulating rubber gloves with leather protectors, disconnect the DC cable for the DC/DC Converter and APG at the PEC.
- With the key off, temporarily remove the Lockout Bracket and pull the Service Switch out.
- Key on.
- Is Fault Code 116 FMI 10 still Active in ServiceRanger?
- If Fault Code 116 FMI 10 is Active with the DC/DC Converter and APG disconnected, go to Step 4.
- If Fault Code 116 FMI 10 is no longer Active with the DC/DC Converter and APG disconnected, key off and reinstall the Lockout Bracket on the PEC. Replace the Power Electronics Carrier (PEC), then go to Step 10.
STEP 4. Verify continuity of PEC connector circuits to ground.
- Key off.
- Disconnect the PEC 19-Way Connector.
- Temporarily remove the Lockout Bracket and pull the Service Switch out.
Note: Ensure the Key Switch is off. - Measure resistance at the PEC 19-Way Connector Terminal at the following pins:
- Pin 17 to Pin 19
- Pin 9 to Pin 11
- Pin 13 to Pin 15
- If the resistance between Pins 17 and Pin 19 is 112–122 ohms and the resistance from Pin 9 to Pin 11 and Pin 13 to Pin 15 are each 33–37 ohms, go to Step 5.
- If resistance is out of range, go to Step 6.
STEP 5. Verify continuity of Inverter connector circuits to ground.
- Key off.
- Reconnect the PEC 19-Way Connector.
- Disconnect the Inverter 56-Way Connector.
- Inspect the connector pins for damaged, corroded and/or loose wires.
- Measure resistance between the Inverter 56-Way Connector at the following pins:
- Pin 29 to Pin 37
- Pin 30 to Pin 35
- Pin 31 to Pin 36 Note: Gently flex the Inverter 56-Way Connector Harness near the Connector while monitoring the resistance values.
- If the resistance between Pin 29 and Pin 37 is 112–122 ohms and the resistance from Pin 30 to Pin 35 and Pin 31 to Pin 36 are each 33–37 ohms, push the Service Switch on the PEC and reinstall the Lockout Bracket. Go to Step 8.
- If resistance is out of range, repair the Hybrid Harness between the PEC and Inverter, then go to Step 10.
STEP 6. Verify continuity of PEC connector circuits.
- Key off.
- Remove the Air Filter Cover and Air Filter from the PEC. Refer to TRSM1000 for procedures.*
- An Inertia Switch is located at the front of the PEC inside the box and viewable when the Air Filter is removed.
- Using ASTM Class 0 electrical insulating rubber gloves with leather protectors, press the button on the top of the Inertia Switch until heard or felt a click. This switch must be depressed a set distance to reset the switch.
- Measure resistance at the PEC 19-Way Connector Terminal at the following pins:
- Pin 17 to Pin 19
- Pin 9 to Pin 11
- Pin 13 to Pin 15
- qIf the resistance between Pin 17 and Pin 19 is 112–122 ohms and the resistance from Pin 9 to Pin 11 and Pin 13 to Pin 15 are each 33–37 ohms, the Inertia Switch was tripped. Test is complete. Go to Step 10.
- If resistance is out of range, push in the Service Switch on the PEC and reinstall the Lockout Bracket, then go to Step 7.
STEP 7. Verify continuity of Inverter connector circuits.
- Key off.
- Disconnect the DC High-Voltage Cable at the PEC Bulkhead and at the Inverter Bulkhead.
- Measure resistance between the Low-Voltage Interlock Pins on the PEC side of the DC High-Voltage Cable:
Note: The Interlock Pins are the two small spade terminals located in the same opening.- If the resistance is 0–0.3 ohms between the Interlock Loop Pins, replace the Power Electronics Carrier (PEC), then go to Step 10.
- If resistance is out of range, replace the DC high-voltage cable, then go to Step 10.
STEP 8. Verify continuity of DC Cable from PEC to Inverter Connector circuits.
- Key off.
- Disconnect the DC High-Voltage Cable at the PEC Bulkhead and the Inverter Bulkhead.
- Measure the resistance of each high-voltage circuit on the cable:
- If the resistance of each high-voltage circuit in the cable is 1 ohm or less, replace the Inverter, then go to Step 10.
- If resistance is out of range, replace the DC High-Voltage Cable, then go to Step 10.
STEP 9. Verify Data Monitor parameters.
- Connect ServiceRanger to the 9-Way Diagnostic Connector in the cab.
- Select the “Data Monitor” option.
- View the following parameters in the High-Voltage Battery list.
- Battery Pack Voltage (BCU1) PID 118
- Battery Voltage PID 116
- If the voltage readings on PID 116 and PID 118 are within 10 volts of each other, replace the Power Electronics Carrier (PEC), then go to Step 10.
- If the voltage readings on PID 116 and PID 118 are greater than 10 volts of each other, replace the Inverter, then go to Step 10.
STEP 10. Verify repair.
- Key off.
- Reconnect all connectors and the negative battery cable.
- Key on.
- Clear codes, see Clear Inactive Faults.
- Drive the vehicle and attempt to reset the code.
- Check for codes, see View Active and Inactive Faults.
- If no codes, test is complete.
- If Fault Code 116 appears, contact Eaton at 1- 800-826-HELP (4357). Repeat this Step (Step 10).
- If a code other than 116 appears, see Fault Code Index List.
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