Eaton Fuller Hybrid Fault Code 17 – Start Enable 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 Start Enable Relay is wired into the Transmission Electronic Control Unit (TECU) on the coil side of the relay. At key on, the HCM determines which starting method to use (high-voltage Motor/Generator or Engine Starter). If the HCM uses the standard engine Starter, the 12-volt Cranking Relay is energized supplying battery power to the Start Enable Relay main feed, which then powers the Starter Solenoid.

Fault Code 17 – Start Enable Relay Detection

The following preconditions must be met before the system detects the fault:

  • Transmission Electronic Control Unit (TECU) ignition voltage is greater than 7 volts and less than 16 volts.

Conditions to Set Fault Code Active

  • FMI 3: TECU detects an open or short to VBATT in the control circuit of the Start Enable Relay for 1 second or greater.
    FMI 4: TECU detects a short to ground in the control circuit of the Start Enable Relay for 1 second or greater.

Fallback When Fault Code 17 is set the following conditions occur:

  • Red “Service” light illuminates and an “F” flashes in the gear display.
  • Fault is stored in TECU memory.
  • If the fault sets at power up the engine still cranks, provided the high-voltage batteries have a sufficient State of Charge (SOC).
  • If the fault sets while driving, the vehicle continues to operate.

Conditions to Set Fault Code Inactive

Only Inactive faults can be cleared from the TECU or HCM history using ServiceRanger. The TECU automatically clears the faults from history after 200 hours. The HCM automatically clears a fault from history after it has been Inactive for 200 hours.

This fault code can be caused by any of the following:

  • FMI 3, 4
    • Loose or corroded connections, bent or burnt pins, short to ground, open, or short to VBATT on the circuit.
    • Start Enable Relay
    • TECU

Fault Code 17 – Start Enable Relay Test

Component Identification:

Harness Front View TECU - Vehicle Interface Connector

Front Harness View
(TECU – Vehicle Interface Connecto

Relay switch

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.

Eaton Fuller TECU start enable relay connection

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