Eaton Fuller Hybrid Transmission Fault Code 38 – Battery Fan 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 Battery Fan Relay is normally an open relay connected to the Hybrid Control Module (HCM) on the control side. When the HCM powers the control circuit, it closes the relay contacts and turns on the relay. The Battery Fan Relay powers the Battery Fan located in the Power Electronics Carrier (PEC), cooling the high-voltage batteries.
Fault Code 38 – Battery Fan 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
Conditions to Set Fault:
• FMI 3 is set when the sensor voltage is greater than 4.1 volts for 10 seconds, while the Inverter temperature is over 35 °C or 95 °F, or if the sensor output voltage is less than 0.2 volts for 10 seconds.
Fallback When Fault Code 38 is set the following conditions occur:
- FMI 3 is set when the HCM detects a short to battery in the coil circuit of the Battery Fan Relay.
- FMI 4 is set when the HCM detects a short to ground in the coil circuit of the Battery Fan Relay.
- FMI 5 is set when the HCM detects an open in the coil circuit of the Battery Fan Relay.
- FMI 14 is set when the following conditions are true for 10 minutes:
- High-voltage battery temperature is greater than 131 °F (55 °C)
- Difference between the minimum and maximum battery temperatures is less than 33 °F (1 °C)
- No battery temperature faults from the Battery Control Module
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 from HCM to Battery Fan Relay
- Battery Fan Relay
- FMI 14
- Battery Fan Relay
- Battery Fan
- Plugged Air Filter
- Battery Fan Relay main power supply
Fault Code 38 – Battery Fan Relay Test
Front Harness View
HCM – Hybrid System Interface Connecto
Harness Connector View
(PEC 19 – Way)
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.
Any transmission part you need we have it! Same day shipping available, worldwide.
NEED FREE SUPPORT FROM ONE OF OUR EXPERTS?