Fault Code 775: Rail D Operation (TRTS0950)

Endurant HD

TRTS0950 EN-US

September 2024 - B

Fault Code 775: Rail D Operation

J1939: SA 3 SPN 6147 FMI 0, 1, 2, 7, 10, 14, 15, 16, 17, 18, 20, 21

Overview

The Mechatronic Transmission Module (MTM) is equipped with solenoids to direct pneumatic flow to actuate shift rails and sensors to monitor rail positions. The Transmission Control Module (TCM) compares the rail command and position to ensure proper rail operation. The solenoids, positions sensors and shift rails are located in the MTM and connected to the TCM at the 74-Way Transmission Harness Connector.

Detection

The TCM monitors the Rail D Operation. 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): Rail D is unable to disengage the Primary Driven Gear, move aft, for 2 seconds.

FMI 1 – Data Valid But Below Normal (Most Severe): Rail D is unable to disengage the Reverse Gear, move fore, for 2 seconds.

FMI 2 – Data Erratic: Rail D is unable to move the sliding clutch to neutral during a rail calibration.

FMI 7 – Mechanical System Not Responding: Rail D is unable move from neutral toward the Primary Driven Gear for 2 seconds.

FMI 10 – Abnormal Rate of Change: Rail D is unable to confirm low rail speed velocity during a rail calibration.

FMI 14 – Special Instructions: Rail D is unable to move from neutral toward the Reverse Gear for 2 seconds.

FMI 15 – Data Valid but Above Normal (Least Severe): Rail D is unable to fully engage the Primary Driven Gear for 2 seconds.

FMI 16 - Data Valid but Above Normal (Moderately Severe): Rail D is unable to achieve neutral from the Primary Driven Gear for 2 seconds.

FMI 17 – Data Valid but Below Normal (Least Severe): Rail D is unable to fully engage the Reverse Gear for 2 seconds.

FMI 18 – Data Valid but Below Normal (Moderately Severe): Rail D is unable to achieve neutral from the Reverse Gear for 2 seconds.

FMI 20 – Data Drifted High: Rail D travel was greater than expected during a rail calibration.

FMI 21 – Data Drifted Low: Rail D travel was less than expected during a rail calibration.

Fallback

FMI 0, 1:

Amber warning lamp on
Rail D movement prohibited

FMI 2, 10, 20, 21:

Amber warning lamp on
Rail D movement prohibited
Non neutral modes prohibited
PTO Mode prohibited
If the vehicle is moving
- Red stop lamp on

FMI 7, 15:

Amber warning lamp on
Rail D engagement of the Primary Driven Gear prohibited
If vehicle is moving and no start gear available
- Red stop lamp on

FMI 14, 17:

Amber warning lamp on
Rail D engagement of the Reverse gear prohibited
If vehicle is moving and no start gear available
- Red stop lamp on
Amber warning lamp on
Rail D engagement of the sliding clutch into neutral prohibited

FMI 16, 18:

If vehicle is moving
- Rail D movement prohibited
If vehicle is moving and no start gear available
- Red stop lamp on

Conditions to Set Fault Code Inactive

FMI 0, 1, 7, 14, 16, 18: Condition no longer exists

FMI 2, 10, 20, 21: Successful rail calibration

FMI 15, 17: Key cycle

Possible Causes

FMI 0:

Transmission PTO
- Not properly configured in TCM
- Not properly wired or installed
- Always engaged
MTM
- Contamination from vehicle air system
- Air leaks
- Rail D Fore Solenoid - internal failure
- Rail D Aft Solenoid - internal failure
- Rail D Position Sensor - in range internal failure
- Rail D shift cylinder - stuck piston or damaged seals
- Rail D shift rail or yoke - broken
Internal transmission
- Rail D Sliding Clutch
- Driven Gear 1st
- Reverse Gear

FMI 1, 2, 7, 10, 14, 16, 18, 20, 21:

MTM
- Contamination from vehicle air system
- Air leaks
- Rail D Fore Solenoid - internal failure
- Rail D Aft Solenoid - internal failure
- Rail D Position Sensor - in range internal failure
- Rail D shift cylinder - stuck piston or damaged seals
- Rail D shift rail or yoke - broken
Internal transmission
- Rail D Sliding Clutch
- Driven Gear 1st
- Reverse Gear

FMI 15, 17:

MTM
- Contamination from vehicle air system
- Air leaks
- Rail D Fore Solenoid - internal failure
- Rail D Aft Solenoid - internal failure
- Rail D Position Sensor - in range internal failure
- Rail D shift cylinder - stuck piston or damaged seals
- Rail D shift rail or yoke - broken
Internal transmission
- Rail D Sliding Clutch
- Primary Driven Gear
- Reverse Gear
Clutch Assembly
TCM
- Software Issue

Additional Tools

Endurant HD Service Manual TRSM0950

Component Identification


1. Transmission Control Module (TCM) Cover 2. Transmission Control Module (TCM) 3. 74-Way Transmission Harness Connector (MTM-side) 4. 74-Way Transmission Harness Connector (TCM-side) 5. Transmission Control Module (TCM) Seal 6. MTM Air Inlet Port

_Graphics/LineArt/TRTS0950_FC511_ComponentID.png

1. Transmission Control Module (TCM) Cover

2. Transmission Control Module (TCM)

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

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

5. Transmission Control Module (TCM) Seal

6. MTM Air Inlet Port

Fault Code 775 Troubleshooting

Purpose:Check for active or inactive fault codes.

Set vehicle parking brake and chock wheels.
Record the transmission fault codes, FMIs, occurrences, and timestamps from the Service Activity Report created during the Diagnostic Procedure.

If Fault Code 775 FMI 0, is Active or Inactive, Go to Step B

If Fault Code 775 FMI 1, is Active or Inactive, Go to Step C

If Fault Code 775 FMI 2, 7, 10, 14, 16, 18, 20, 21 is Active or Inactive, Go to Step D

If Fault Code 775 FMI 15, 17 is Active or Inactivez, go to TAIB-1004 Fault Code 775 Rail D Operation FMI 15/17 - Endurant HD.

Purpose:Inspect for a Transmission PTO.

Inspect for a transmission mounted PTO.

If transmission is not equipped with a PTO, Go to Step C

If transmission is equipped with a PTO:

Verify PTO operation and installation: Properly wired and configured in TCM.

Note: After PTO inspection: -If PTO issue is found repair as needed, refer to TRIG2610 Endurant HD PTO Installation Guide. Recheck for fault codes. -If no PTO issue found, go to Step C .

Purpose:Verify MTM Serial Number.

Record MTM Serial Number (Item 2).

If MTM Serial Number is less than 12S22342093445, go to Endurant HD Service Manual TRSM0950 Appendix MTM Rail B, C and D Cylinder Inspection Procedure.

If MTM Serial Number is equal to or greater than 12S22342093445, Go to Step D

Purpose:Verify condition of the vehicle air system supply line and MTM air inlet port.

Key off.
Refer to OEM guidelines and vent the vehicle air supply line to the MTM.
Refer to OEM guidelines and remove the vehicle air supply line at the MTM.
Inspect the vehicle air supply line and the MTM air inlet port for contamination, moisture, corrosion and/or debris.
Note: Verify the MTM inlet screen is installed and free of contamination and/or debris.

If contamination is found, refer to OEM guidelines for repair or replacement of the vehicle air system. Replace the Mechatronic Transmission Module (MTM) and reference the Lower Countershaft Cover and Inertia Brake Service Procedure for replacement of the Inertia Brake Assembly. Go to Step V

Note: MTM removal and installation requires the transmission to be removed from the vehicle. Reference Endurant HD Service Manual TRSM0950, Transmission Removal Service Procedure.

If no contamination is found, Go to Step E

Purpose:Verify mechanical condition of the Primary Driven Gear and Reverse Gear.

Remove the MTM.
Note: MTM removal and installation requires the transmission to be removed from the vehicle. Reference Endurant HD Service Manual TRSM0950, Transmission Removal Service Procedure.
Inspect the Primary Driven Gear for excessive fore and aft movement.
Inspect the Reverse Gear for excessive fore and aft movement.

If excessive gear movement is evident, inspect for cause of excessive gear movement and repair. Go to Step V

If no excessive gear movement is evident, Go to Step F

Purpose:Verify mechanical condition of the Rail D Sliding Clutch and clutching teeth.

Inspect the Rail D Sliding Clutch yoke slot for wear.
Shift the Rail D Sliding Clutch to the neutral position (if necessary).
Shift the Rail D Sliding Clutch into the Primary Driven Gear engagement position (fore).
Inspect the Rail D Sliding Clutch clutching teeth for wear.
Return the Rail D Sliding Clutch to neutral.
Shift the Rail D Sliding Clutch into the Reverse Gear engagement position (aft).
Inspect the Rail D Sliding Clutch clutching teeth for wear.
Return the Rail D Sliding Clutch to neutral.

If the Rail D Sliding Clutch shifts into all three positions and no clutching teeth wear is present, replace the Mechatronic Transmission Module (MTM). Go to Step V

If the Rail D Sliding Clutch does not shift into all three positions or clutching teeth wear is present, replace the Rail D Sliding Clutch, Primary Driven Gear, Reverse Gear and Mechatronic Transmission Module (MTM). Go to Step V

Purpose:Verify repair.

Key off.
Reconnect all connectors and verify that all components are properly installed.
Key on with engine off.
Connect ServiceRanger.
Go to “Fault Codes”.
Select “Clear All Faults”.
Operate vehicle and attempt to reset the fault code or duplicate the previous complaint.
Check for fault codes using ServiceRanger.

If no fault codes set and the vehicle operates properly, test complete.

If Fault Code 775 sets Active during operation, Go to Step A

If a fault code other than 775 sets Active, troubleshoot per the Fault Code Isolation Procedure Index.