Eaton Fuller Hybrid Transmission Fault Code 33 – Low Battery Voltage (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 to control the transmission operation; however, the Hybrid Control Module (HCM) controls the operation of the TECU during normal hybrid mode operation. The HCM main battery power is a fused 12-volt feed that runs through the HCM 38-Way Vehicle Connector with the main ground wire returning to the battery negative terminal.

Fault Code 33 – Low Battery Voltage (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.

Conditions to Set Fault Code Active

  • FMI 4 is set when the TECU battery voltage drops below 7 volts for more than 1 second.

Fallback When Fault Code 33 is set the following conditions occur:

  • Fault is stored in TECU memory.
  • No lights are illuminated on the Push Button.
  • If this fault occurs prior to power up, the vehicle will not crank.
  • If this fault occurs while driving, the vehicle maintains current gear. Clutch opens when the vehicle stops.

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 4
    • Power supply to TECU
    • Low batteries or bad main power connection
    • Charging system
    • TECU

Fault Code 33 – Low Battery Voltage Test

Component Identification MY08 System:

Fuller Harness Front View TECU - Vehicle Interface Connector

Harness Front View (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.

Eaton Fuller TECU to battery connector

STEP 1. Check for Active or Inactive fault code status and perform Electrical Pretest.

  1.  Retrieve Active fault codes and FMIs with ServiceRanger using the 9-Way Diagnostic Connector.
  2. Perform Electrical Pretest.
    • If Fault Code 33 is Active after performing the Electrical Pretest, replace Transmission Electronic Control Unit (TECU) (only if fault code is Active),  then go to Step 2.
      • If Fault Code 33 is Inactive after performing the Electrical Pretest, clear codes and go to Step 2.

STEP 2. Verify repair.

  1. Key off.
  2.  Reconnect all connectors and negative battery cable.
  3. Key on.
  4. Clear codes, see  Clear Inactive Faults.
  5. Drive the vehicle and attempt to reset the code.
  6. Check for codes, see View Active and Inactive Faults.
    • If no codes, test is complete.
    • If fault Code 3 appears, find error in testing, go to Step 1.
    • If a code other than 3 appears, see Fault Code Index List.

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