Eaton Fuller Hybrid Transmission Fault Code 48 – J1939 Transmission Message (HCM)
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 and International truck. J1939 is a high-speed twisted pair 250K data link with one 120 ohm resistor at each end of the link. The Hybrid Control Module (HCM) is connected to the J1939 data link at the 38-Way Connector. This link transmits information to the HCM and communicates with other modules on the network such as the Transmission Electronic Control Unit (TECU).
Fault Code 48 – J1939 Transmission Message (HCM) Detection
The following preconditions must be met before the system detects the fault:
- HCM ignition voltage is greater than 7 volts and less than 16 volts.
- J1939 data link communication fault is Inactive.
Note: When troubleshooting an Inactive code refer to the Product Diagnostic Mode (PDM)
Conditions to Set Fault Code Active
- FMI 9 is set when the HCM fails to receive TECU data for 30 consecutive messages or greater, while it continues communicating with other modules on J1939.
Fallback When Fault Code 48 is set the following conditions occur:
- Amber “Check Hybrid” light illuminates.
- Fault is stored in HCM memory.
- Red “Service” light may illuminate and a “F” may flash in the gear display due to an Active Fault Code 24.
- Operation mode changes to “AutoShift Only” mode.
- Electric Motor/Generator Assist and Regeneration are disabled; however, the high-voltage relays remain powered.
- If the fault sets at power up, the engine will not crank.
- If the fault sets while driving, the vehicle will shift; however, when the vehicle stops the clutch opens and remains in the open position.
- 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 2, 9
- J1939 Data Link
Fault Code 48 – J1939 Transmission Message (HCM) Test
Harness Front View
(TECU – Vehicle Interface Connector
Harness Front View
(HCM – Vehicle Interface Connector)
NOTE: Refer to the Eaton Hybrid Component and Connector Location for Connector Locations in MY08 Systems
NOTE: Refer to the Eaton Hybrid Component and Connector Location for Connector Locations in MY09 Systems.
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