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 batteries are 172 volts each connected in series to produce 340 volts DC. The Battery Control Unit, located in the Relay Box, communicates with each battery to determine temperature, State Of Charge (SOC) and voltage. This information is then sent to the Inverter.
Eaton Fuller Hybrid Transmission Fault Code 77 High Voltage Battery 2 Potential Voltage 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.
- Battery Control Unit 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 high-voltage battery is greater than 417 volts for 240 MS.
- FMI 16 is set when the BCU detects the high-voltage battery is greater than 408 volts for 240 MS.
- FMI 4 is set when the BCU detects the high-voltage battery is less than 211 volts for 240 MS.
- FMI 18 is set when the BCU detects the high-voltage battery is less than 240 volts for 240 MS.
Fallback When Fault Code 77 is set the following conditions occur:
- Amber “Check Hybrid” light blinks for FMI 4 and displays solid for FMI 3
- 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 3, 4
- DC cable
- DC Interlock Loop
- Service Switch
- Inertia Switch