Endurant XD
TRTS0960 EN-US
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September 2024 - A

Fault Code 646: Rail E Fore Solenoid (A6)

J1939: SA 3 SPN 768 FMI 0, 1, 3, 4, 5, 6, 7, 8, 12, 16, 17, 18

Overview

The Endurant XD Series transmissions are equipped with solenoid valves that direct vehicle Supply Air to and from the shift rail cylinders in the Mechatronic Transmission Module (MTM). Movement of each shift rail is controlled 2 solenoids; a Fore and a Aft.

The Rail E Fore Solenoid (REFS) valve is energized by the Transmission Control Module (TCM) to direct Supply Air to the Shift Rail E Cylinder to move the Rail E Shift Yoke and Rail E Synchronizer in the fore or forward direction. The REFS valve is located in the MTM and connected to the TCM at the 74-Way Transmission Harness Connector.

Detection

The TCM monitors the REFS circuit and Shift Rail E position. If a system failure is detected, the fault is set Active.

Conditions to Set Fault Code Active

FMI 0 – Data Valid But Above Normal (Most Severe): REFS Low-Side Current value greater than commanded current for 1 second.

FMI 1 – Data Valid But Below Normal (Most Severe): REFS Low-Side Current value less than commanded current for 1 second.

FMI 3 – Voltage Above Normal or Shorted High: REFS circuit shorted to power for 2 seconds after REFS commanded off.

FMI 4 – Voltage Below Normal or Shorted Low: REFS circuit shorted to ground for 2 seconds after REFS commanded off.

FMI 5 – Current Below Normal or Open Circuit: REFS circuit open for 2 seconds after REFS commanded off.

FMI 6 – Current Above Normal or Shorted Circuit: REFS circuit shorted to ground for 2 seconds after REFS commanded on.

FMI 7 – Mechanical System Not Responding: Rail E Position value and speed sensors confirmed uncommanded movement from Low Range toward neutral position.

FMI 8 – Abnormal Frequency: REFS signal frequency out of range for 1 second.

FMI 12 – Bad Intelligent Device: TCM detected an internal processing error.

FMI 16 – Data Valid but Above Normal (Moderately Severe): REFS commanded on longer than expected increasing solenoid temperature.

FMI 17 – Data Valid but Below Normal (Least Severe): Rail E Position value and speed sensors confirmed uncommanded movement from Low Range toward neutral position.

FMI 18 – Data Valid but Below Normal (Moderately Severe): REFS circuit voltage lower than expected for 1 second after REFS commanded on.

Fallback

FMI 0, 1, 3, 4, 5, 6, 8, 12, 16, 18:

  • Amber warning lamp on
  • Shift Rail E movement in the fore direction prohibited

FMI 7:

  • No degraded modes

FMI 17:

  • Amber warning lamp on
  • Low Range engagement prohibited

Conditions to Set Fault Code Inactive

FMI 0, 1, 6, 7, 8, 12, 16, 17, 18: Key cycle and fault condition no longer exists.

FMI 3: REFS circuit not shorted to power for 10 seconds.

FMI 4: REFS circuit not shorted to ground for 10 seconds.

FMI 5: REFS circuit not open for 10 seconds.

Possible Causes

FMI 0, 1, 3, 4, 5, 6, 8, 16, 18:

  • MTM - REFS
    • Internal failure
    • Damaged
  • MTM - Transmission Harness
    • Wiring shorted to power, shorted to ground or open
  • TCM
    • Internal failure

FMI 7, 17:

  • MTM - REFS
    • Partially stuck open
  • Internal transmission
    • Rail E Detent
    • Rail E Synchronizer

FMI 12:

  • TCM
    • Software issue
    • Internal failure

Additional Tools

  • Endurant XD Service Manual TRSM0960
  • Eaton Breakout Box with 74-Way Eaton Diagnostic Adapter - RR1029TR
  • Digital Volt/Ohm Meter (DVOM)
  • MTM Alignment Tool (RR1086TR-1)

Component Identification

_Graphics/LineArt/TRTS0960_FC275_ComponentID.png

1. Transmission Control Module (TCM) Cover

2. Transmission Control Module (TCM)

3. 74-Way Transmission Harness Connector (TCM-side)

4. 74-Way Transmission Harness Connector (MTM-side)

5. Transmission Control Module (TCM) Seal

6. Mechatronic Transmission Module (MTM)

Fault Code 646 Troubleshooting

A
Purpose:Check for active or inactive fault codes.

  1. Set vehicle parking brake and chock wheels.

  2. Key off.

  3. Record transmission fault codes, FMIs, occurrences, and timestamps from Service Activity Report created during the Diagnostic Procedure.

  • If Fault Code 646 FMI 0, 1, 3, 4, 5, 6, 8, 16, 18 is Active or Inactive, Go to Step B

  • If Fault Code 646 FMI 12 is Active or Inactive, Contact Eaton Cummins Automated Transmission Technologies for further diagnostic instructions. For Help Line phone numbers, go to Contact Information. Go to Step V

  • If Fault Code 646 FMI 7, 17 is Active or Inactive, Go to Step E

B
Purpose:Verify condition of TCM 74-Way Connector.

  1. Key off.

  2. Remove TCM from MTM with 20-Way TCM Vehicle Harness Connector and 20-Way TCM Body Harness Connector connected.

    _Graphics/LineArt/TRTS0950_FC511_Check74WayTCM.png

  3. Inspect TCM side of the 74-Way Transmission Harness Connector, verify connector is free from contamination and corrosion; terminals are not bent, spread or loose; and there is no damage to connector body.

  4. Inspect TCM Seal, verify seal is properly installed and not damaged.

C
Purpose: Verify Rail E Fore Solenoid resistance and not shorted to ground.

  1. Key off.

  2. Connect Eaton Breakout Box with 74-Way Eaton Diagnostic Adapter to MTM side of 74-Way Transmission Harness Connector.

    _Graphics/LineArt/TRTS0950_FC511_74WaytoMTM.png

  3. Measure resistance at Eaton Breakout Box between Pin 62 and Pin 63. Record reading in table.

    _Graphics/LineArt/TRTS0960_FC646_DVOM62and63ohms.png

  4. Measure resistance at Eaton Breakout Box between Pin 63 and Ground (TCM mounting stud). Record reading in table.

    _Graphics/LineArt/TRTS0960_FC646_DVOM63andGroundohms.png

  5. Compare reading(s) in table.

PinsRangeReading(s)
62 to 633.4–5.5 Ohms
63 to ground (TCM mounting stud)Open Circuit (OL)
D
Purpose:Check for Active or Inactive fault codes.

  1. Key off.

  2. Remove Eaton Breakout Box 74-Way Eaton Diagnostic Adapter.

  3. Reinstall TCM to MTM.

  4. Reconnect all connectors and verify all components are properly installed.

  5. Key on with engine off.

  6. Connect ServiceRanger.

  7. Retrieve and record transmission fault codes, FMIs, occurrences, and timestamps.

E
Purpose:Verify mechanical movement of Rail E Range Synchronizer.

  1. Key off.

  2. Remove MTM.

    Note: MTM removal and installation requires transmission be removed from vehicle. Reference Endurant XD Service Manual TRSM0960, Transmission Removal Service Procedure.

  3. Install MTM Alignment Tool (RR1086TR-1) onto main housing.

    Note: Reference Appendix/Manually Actuate Rail E Procedure.

  4. Using Rail E Lever, shift Rail E into neutral position (if necessary).

  5. Shift Rail E into High Range engagement position (fore) and return to neutral position.

  6. Shift Rail E into Low Range engagement position (aft) and return to neutral position.

  • Contact Eaton Cummins Automated Transmission Technologies at +1 800-826-4357 for further diagnostic instructions. Go to Step V

V
Purpose:Verify repair.

  1. Key off.

  2. Reconnect all connectors and verify all components are properly installed.

  3. Key on with engine off.

  4. Connect ServiceRanger.

  5. Go To “Fault Codes”.

  6. Select “Clear All Faults”.

  7. Operate vehicle and attempt to reset the fault code or duplicate the previous complaint.

  8. Check for fault codes using ServiceRanger.