Eaton Fuller Hybrid Transmission Fault Code 39 Heat Exchanger Relay
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. The Heat Exchanger Fan Relay is an open relay connected to the Hybrid Control Module (HCM) on the control side.
When the HCM turns on the relay, it powers the control circuit, closing the relay contacts. The Heat Exchange Fan Relay powers the Heat Exchanger Fan located on the hybrid liquid cooling system radiator. The fan provides additional airflow in certain situations such as slow driving or ePTO operation.
Fault Code 39 – Heat Exchanger Relay 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.
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 HCM detects a short to battery in the coil circuit of the Heat Exchanger Fan Relay.
- FMI 4 is set when the HCM detects a short to ground in the coil circuit of the Heat Exchanger Fan Relay.
- FMI 5 is set when the HCM detects an open in the coil circuit of the Heat Exchanger Fan Relay.
Fallback When Fault Code 39 is set the following conditions occur:
• Amber “Check Hybrid” light illuminates.
• Fault is stored in Hybrid Control Module (HCM) memory.
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, 5
- Vehicle harness form HCM to Heat Exchanger Relay
- Heat Exchanger Relay
- Heat Exchanger Relay fuse
Fault Code 39 – Heat Exchanger Relay Test
Harness Front View
(HCM – Hybrid System Interface Connector)
Typical Relay Switch
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.