Fault Code 72: Failed to Select Rail
J1587: MID 130 SID 59 FMI 7
J1939: SA 3 SPN 772 FMI 7
Overview
The UltraShift PLUS transmission uses the X-Y Shifter to engage and disengage a gear based on the driver’s selected mode of operation. Rail selection is achieved by activating the X-Y Shifter Rail Motor, which controls the lateral movement of the X-Y Shift Finger within the Shift Bar Housing. Certain shifts require the transmission to engage a different rail on the Shift Bar Housing. These rail shifts require the X-Y Shifter to move to Neutral prior to selecting another rail and allowing the next gear engagement. The Shift Bar Housing Interlock physically prevents the engagement of two gears at the same time.
Fault Code 72 sets when the X-Y Shift Finger attempts to move to a different rail position, but the X-Y Rail Position Sensor indicates that the transmission was unable to select the next rail position. Transmission Electronic Control Unit (TECU) detected a system failure, but was unable to detect the specific root cause.
Detection
This fault can only be detected when there are no failures of the TECU, X-Y Gear or Rail Motors, X-Y Position Sensors or Battery Supply voltage. This fault code is set when the system is unable to move to a different rail position and the transmission is not engaged in a gear.
Conditions to Set Fault Code Active
FMI 7 – Mechanical System Not Responding: After being unable to select a rail position for 2 seconds, the fault code sets Active.
Fallback
FMI 7:
- Transmission may not be able to complete a shift to the proper rail.
- Transmission will attempt to move the Shift Finger to the proper rail.
- Gear display may flash current or destination gear.
Conditions to Set Fault Code Inactive
FMI 7: The system successfully positions the Shift Finger on the proper rail.
Possible Causes
FMI 7:
- Vehicle Power Supply
- Poor power or ground supply to TECU
- Bent, spread, corroded or loose terminals
- Vehicle Batteries
- Internal failure
- Transmission Harness
- Damaged wiring between the TECU and X-Y Shifter
- Bent, spread, corroded or loose terminals
- X-Y Shifter
- Worn or damaged X-Y Shifter ball screw, center shaft bushing, or other internal components
- Contaminated X-Y Shifter ball screw due to coolant leak or oil contamination
- Bent, spread, corroded or loose terminals
- Mechanical Transmission
- Worn or damaged Shift Bar Housing
- Worn Sliding Clutch slot width
- Worn or damaged Shift Yokes
- Worn or damaged internal transmission components
Component Identification
 |
1. Transmission Electronic Control Unit (TECU) 2. 38-Way Transmission Harness Connector 3. Gear Position Sensor 4. 3-Way Gear Position Sensor Connector 5. 2-Way Gear Motor Connector (blue) 6. 2-Way Gear Motor Connector Body (blue) |
 |
1. X-Y Shifter 2. 2-Way Rail Motor Connector (black) 3. 2-Way Rail Motor Connector Body (black) 4. 3-Way Rail Position Sensor Connector 5. Rail Position Sensor 6. 38-Way Vehicle Harness Connector |
Fault Code 72 Troubleshooting
Record the transmission fault codes, FMIs, occurrences, and timestamps from the Service Activity Report created during the Diagnostic Procedure.
Note: If Fault Code 72 is Inactive and there are other Active fault codes, troubleshoot all Active fault codes first.
If Fault Codes 33, 34, 51, 52, 61, 63 or 64 are Active or Inactive, troubleshoot per Fault Code Isolation Procedure Index.
If Fault Code 72 is Inactive, Go to Step B
If Fault Code 72 is Active, Go to Step C
Set parking brake and chock wheels.
Place transmission in PD Mode. See more about Product Diagnostic (PD) Mode.
Note: Fault Code 72 does not set Active during PD Mode. Other fault codes may set Active during PD Mode that could indicate an issue with the wiring.
Note: Transmission does not enter PD Mode when Active fault codes exist.
Wiggle wiring and connections of the Transmission Harness from the X-Y Shifter to the TECU.
Wiggle wiring and connections of the Vehicle Power Supply Harness from the batteries to the TECU.
Exit PD Mode by powering down.
Notice
If any fault code sets Active while wiggling the Transmission Harness, replace Transmission Harness. Go to Step V
If any fault code sets Active while wiggling the Power Supply Harness, refer to OEM guidelines for repair or replacement of power supply wiring. Go to Step V
If no fault codes set Active, Go to Step C
Key off.
NoticeInspect Starter, battery terminals and transmission 30-amp In-line Fuse Holder Connections for corrosion, loose terminals and bent or spread pins.
Inspect Battery Positive (+) and Negative (-) wires from the batteries to the TECU including all connections. Ensure a clean ground connection on the chassis. Verify no damage or corrosion to connectors.
If damage is found, repair or replace Power Supply Harness per OEM guidelines. Go to Step V
If no damage is found, Go to Step D
Key off.
Set parking brake and chock wheels.
Load test each vehicle battery per OEM specifications. Record reading(s).
If any battery(s) does not pass the Load Test, refer to OEM guidelines for repair or replacement of battery(s). Go to Step V
If all batteries pass the Load Test, Go to Step E
| Battery | Voltage Drop | Load Test Status (Pass/Fail) |
|---|---|---|
| 1 | ||
| 2 | ||
| 3 | ||
| 4 | ||
| 5 |
Key off.
NoticeInspect the physical condition of X-Y Shifter and all connections.
Inspect Transmission Harness for any pinched, chafed, corroded or shorted wiring.
Disconnect both 2-Way X-Y Gear and Rail Position Sensor Connectors.
Disconnect both 2-Way X-Y Motor Connectors to the Transmission Harness.
Inspect connectors for corrosion, loose terminals, bent or spread pin or damage to the connector bodies.
If damage to the X-Y Shifter or X-Y Shifter wiring is found, replace X-Y Shifter. Go to Step V
If damage to the Transmission Harness is found, replace Transmission Harness. Go to Step V
If no damage is found, Go to Step F
Key off.
Remove the X-Y Shifter.
Inspect condition of the X-Y Shift Finger and Cross Shaft for damage or wear.
Inspect the X-Y Shifter ball screw for signs of coolant contamination.
For the latest Service Bulletin updates, visit Roadranger.com.
If coolant contamination is found, repair the vehicle coolant system leak and follow Service Bulletin TMIB0124 for complete repair procedure. X-Y Shifter must be replaced upon completion of service bulletin. Go to Step V
If damage to the X-Y Shifter is found, replace X-Y Shifter. Go to Step V
If no damage is found, Go to Step G
Key off.
Inspect condition of the Shift Bar Housing Shift Blocks. Look for uneven gaps between the Shift Blocks or excessive wear to the block faces.
Verify Shift Blocks are tight to the rails and there are no other mechanical issues with the Shift Bar Housing.
Verify transmission shifts fully in to and out of each gear.
Test the Shift Interlock to verify that the transmission will not engage two gears at once. See the Shift Interlock Inspection Procedure Shift Interlock Inspection.
If damage to the Shift Bar Housing is found, repair Shift Bar Housing. Go to Step V
If no damage is found, Go to Step H
Key off.
Drain and save the transmission oil. Inspect oil for significant metal fragments.
Remove 8-bolt PTO cover.
Inspect main case gears for damage or excessive movement.
Inspect Shift Yokes and Sliding Clutches for damage or excessive wear.
If damage is found or there are significant metal fragments in the oil, replace damaged, worn or failed transmission components. Go to Step V
If no damage is found within the transmission main case, replace X-Y Shifter and Transmission Harness. Go to Step V
Note: If unsure whether damage or wear is significant, take pictures of the transmission gearing. Ensure these pictures are clear and the components are easily visible. Email these pictures to auto.rtw@eaton.com and contact Eaton at (800) 826-4357.
Key off.
Reconnect all connectors and verify that all components are properly installed, including X-Y Shifter.
Reinstall 8-bolt PTO cover.
Refill transmission with lubricant.
Key on with engine off.
Clear fault codes using ServiceRanger.
Drive vehicle and attempt to reset the code or duplicate the previous complaint.
Check for fault codes using ServiceRanger.
If no fault codes set Active and vehicle operates properly, test complete.
If a fault code other than 72 sets Active, troubleshoot per Fault Code Isolation Procedure Index.
If Fault Code 72 sets Active, refer to Contact Information and contact Eaton for further diagnostics.