Eaton Fuller Hybrid Transmission Fault Code 40 – Cooling Pump 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. Read below to learn how to test, clear and fix fault code errors for your Freightliner, Mack, Peterbilt, Kenworth, Volvo and International truck. The Cooling Pump Relay is 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 Cooling Pump Relay powers the Cooling Pump that circulates the coolant on the hybrid liquid system.
Fault Code 40 – Cooling Pump 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 Cooling Pump Relay.
- FMI 4 is set when the HCM detects a short to ground in the coil circuit of the Cooling Pump Relay.
- FMI 5 is set when the HCM detects an open in the coil circuit of the Cooling Pump Relay.
- FMI 14 is set when the following occur for 10 minutes or longer:
- Inverter temperature is greater than 122 °F (50 °C)
- The difference between the maximum battery temperature and the Inverter temperature is greater than 68 °F (20 °C)
- No battery temperature or motor temperature faults
Fallback When Fault Code 40 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 from HCM to Cooling Pump Relay
- Cooling Pump Relay
- FMI 14
- Cooling Pump Relay
- Cooling Pump
- Cooling Pump Relay main power supply
- Low coolant, Low coolant flow, plugged radiator, fan operation
Fault Code 40 – Cooling Pump Relay Test
Harness Front View
HCM – Hybrid System Interface Connector
(Harness View – Front Side)
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.