Eaton Fuller Hybrid Transmission Fault Code 71 – Failed to Disengage a Gear

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, International, and heavy-duty truck and equipment. The Transmission Electronic Control Unit controls the Electric Shifter, which engages the different rails and gear positions. The Electric Shifter is comprised of two electric motors; one changes the rail position and the other changes the gear position.

Fault Code 71 – Failed to Disengage a Gear 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 System Battery Voltage Low Fault is Inactive.
  • TECU System Battery Voltage Weak Fault is Inactive.
  • TECU J1939 Communication Link Fault is Inactive.
  • J1939 engine torque is zero ± 5% and J1939 engine speed is within 50 RPM of synchronous.

Note: When troubleshooting an Inactive code refer to the Product Diagnostic Mode (PDM)

Conditions to Set Fault Code Active

  • FMI 7 is set when the Electric Shifter fails three consecutive attempts to disengage a gear.

Fallback When Fault Code 71 is set the following conditions occur:

  • Fault is stored in TECU memory
  • If the fault sets while driving, the vehicle maintains the current gear and 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 7
    • Dragging Clutch
    • ECA
    • Shift Bar Housing
    • Electric Shifter
    • Gear Select Sensor
    • Yoke, Sliding Clutch, Mainshaft
    • TECU
    •  Torque locked in gear

Fault Code 71 – Failed to Disengage a Gear Test

Component Identification:

shift forks - Eaton Fuller transmission

The picture above shows the Shift Forks in the neutral position.

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.

STEP 1. Verify gear display in neutral gear position.

  1.  Retrieve Active fault codes and FMIs with ServiceRanger using the 9-Way Diagnostic Connector or manually.
  2. Key on.
  3. Press N on the Push Button Shift Control.
  4. Observe Gear Display:
    •  If gear display shows: “N”, go to Step 5.
    • If gear display shows: “71”, go to Step 2.

STEP 2. Perform Electrical Pretest.

  1. Perform the Electrical Pretest
    • If no issues found during the Electrical Pretest, go to Step 3.
    • If issue was repaired during the Electrical Pretest, go to Step 1.

STEP 3. Perform manual Shift Bar Housing inspection.

  1. Key off.
  2. Remove Electric Shifter* from Shift Bar Housing to see what gear position is currently engaged.
  3. Attempt to move the engaged rail back to neutral:
    • If rails move from the engaged position to neutral, go to Step 4.
    • If rails do not move from the engaged position, attempt to take the torque off the driveline. If concern is still present, inspect the Main Case for a damaged Mainshaft, sliding Clutch, or Fork. Go to Step 5

* See Electric Shifter in Eaton Fuller TRSM1000(MY08)/TRSM2000(MY09) Manual.

STEP 4. Verify integrity of Shift Bar Housing components.

  1. Key off.
  2. Inspect the following:
    • Shift blocks are fastened to Shift Rails securely
    • Electric Shifter is free from any excessive lube contamination buildup
    • Two gear positions can not be engaged at the same time
      • If no problem found, replace the Electric Shifter, then go to Step 5.
      • If problem is found, repair as required, then go to Step 5.

STEP 5. Verify repair.

  1. Key off.
  2. Reconnect all connectors and the 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 71 appears, find error in testing, go to Step 1.
    • If a code other than 71 appears, see Fault Code Index List.

Any transmission part you need we have it! Same day shipping available, worldwide.

NEED FREE SUPPORT FROM ONE OF OUR EXPERTS?

CALL NOW
EMAIL US