Eaton Fuller Hybrid Transmission Fault Code 37 – Power Supply (TECU)
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 Transmission Electronic Control Unit (TECU) is mounted to the transmission and contains the software that controls the transmission operation; however, the Hybrid Control Module (HCM) controls the operation of the TECU during normal hybrid mode. The TECU main battery power is a fused, 12-volt feed that runs through the TECU 38-Way Vehicle Connector with the main ground wire returning to the battery negative terminal.
Fault Code 37 – Power Supply (TECU) Detection
The following preconditions must be met before the system detects the fault:
- TECU ignition voltage is greater than 7 volts and less than 16 volts.
- TECU only runs this test if the Electric Shifter is being cycled from N to gear.
Note: When troubleshooting an Inactive code refer to the Product Diagnostic Mode (PDM)
Conditions to Set Fault Code Active
- FMI 5 is set when the TECU power supply resistance is measured before and during an electric shifter test and the results show a measurement of 0.4 ohms or greater.
Fallback When Fault Code 37 is set the following conditions occur:
- Fault is stored in TECU 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 5
- Power supply to TECU
- Low batteries or bad main power connection
- Broken or corroded battery interconnect straps may also be the cause of high resistance readings
Fault Code 37 – Power Supply (TECU) Test
(TECU – 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.
Warning! – Do Not Load Test at Diagnostic Port
4-Pin Diagnostic Port
(Located at the left rear corner of the transmission.)
B – Service Bat. +
C – Service Bat. –
A – Service Ignition +