Fault Code 637: Rail D Aft Solenoid (B3)
J1939: SA 3 SPN 4216 FMI 0, 1, 3, 4, 5, 6, 7, 8, 12, 14, 15, 16, 17, 18, 31
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 D Aft Solenoid (RDAS) valve is energized by the Transmission Control Module (TCM) to direct Supply Air to the Shift Rail D Cylinder to move the Rail D Shift Yoke and Rail D Sliding Clutch in the aft or rearward direction. The RDAS valve is located in the MTM and connected to the TCM at the 74-Way Transmission Harness Connector.
Detection
The TCM monitors the RDAS circuit and Shift Rail D 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): RDAS Low-Side Current value greater than commanded current for 1 second.
FMI 1 – Data Valid But Below Normal (Most Severe): RDAS Low-Side Current value less than commanded current for 1 second.
FMI 3 – Voltage Above Normal or Shorted High: RDAS circuit shorted to power for 2 seconds after RDAS commanded off.
FMI 4 – Voltage Below Normal or Shorted Low: RDAS circuit shorted to ground for 2 seconds after RDAS commanded off.
FMI 5 – Current Below Normal or Open Circuit: RDAS circuit open for 2 seconds after RDAS commanded off.
FMI 6 – Current Above Normal or Shorted Circuit: RDAS circuit shorted to ground for 2 seconds after RDAS commanded on.
FMI 7 – Mechanical System Not Responding: Rail D Position value and speed sensors confirmed uncommanded movement from Driven Gear 1sst toward neutral position.
FMI 8 – Abnormal Frequency: RDAS signal frequency out of range for 1 second.
FMI 12 – Bad Intelligent Device: TCM has detected an internal processing error.
FMI 14 – Special Instructions: Rail D Position value indicated uncommanded movement from neutral position toward Reverse Gear immediately after a shift into neutral position.
FMI 15 – Data Valid but Above Normal (Least Severe): Rail D Position value indicated uncommanded movement from neutral position toward Reverse Gear for 2 seconds.
FMI 16 – Data Valid but Above Normal (Moderately Severe): RDAS commanded on longer than expected increasing solenoid temperature.
FMI 17 – Data Valid but Below Normal (Least Severe): Rail D Position value and speed sensors confirmed uncommanded movement from Driven Gear 1st toward neutral position.
FMI 18 – Data Valid but Below Normal (Moderately Severe): RDAS circuit voltage lower than expected for 1 second after RDAS commanded on.
FMI 31 – Condition Exists: During a rail calibration, Rail D Position value indicated uncommanded movement from neutral position toward Reverse Gear immediately after a shift into neutral position.
Fallback
FMI 0, 1, 3, 4, 5, 6, 8, 12, 16, 18:
- Amber warning lamp on
- If vehicle is stationary and Shift Rail D is not in the neutral position:
- Shift Rail D movement in the aft direction prohibited
- If vehicle is moving and Shift Rail D is in neutral position:
- Shift Rail D movement prohibited
- If vehicle is moving and no start gear available
- Red stop lamp on
FMI 7:
- No degraded modes
FMI 14:
- Amber warning lamp on
- Shift Rail D movement prohibited
FMI 15:
- Amber warning lamp on
- Urge to Move and Creep Mode prohibited
- Inertia Brake activation prohibited
- Upshifts prohibited
- Clutch engagements prohibited
- Non-Neutral modes prohibited
- PTO Mode prohibited
- If vehicle is moving:
- Red stop lamp on
FMI 17:
- Amber warning lamp on
- Driven Gear 1st engagement prohibited
FMI 31:
If Shift Rail D is not in a fully engaged or fully disengaged position:
- Amber warning lamp on
- Shift Rail D movement prohibited
If Shift Rail D is in a fully engaged or fully disengaged position:
- Shift Rail C movement prohibited
- Shift Rail D movement prohibited
- Inertia Brake activation prohibited
- Clutch engagements prohibited
- Non-Neutral modes prohibited
- PTO Mode prohibited
- If vehicle is moving:
- Red stop lamp on
Conditions to Set Fault Code Inactive
FMI 0, 1, 6, 7, 8, 12, 14, 15, 16, 17, 18, 31: Key cycle and fault condition no longer exists.
FMI 3: RDAS circuit not shorted to power for 10 seconds.
FMI 4: RDAS circuit not shorted to ground for 10 seconds.
FMI 5: RDAS circuit not open for 10 seconds.
Possible Causes
FMI 0, 1, 3, 4, 5, 6, 8, 16, 18:
- MTM - RDAS
- Internal failure
- Damaged
- MTM - Transmission Harness
- Wiring shorted to power, shorted to ground or open
- TCM
- Internal failure
FMI 7, 17:
- MTM - RDAS
- Partially stuck open
- Internal transmission
- Reverse Gear
- Rail D Sliding Clutch
FMI 12:
- TCM
- Software issue
- Internal failure
FMI 14, 15:
- MTM - RDAS
- Partially stuck open
- MTM - Rail D Position Sensor
- Internal failure
FMI 31:
- MTM - RDAS
- Partially stuck open
Additional Tools
- Endurant XD Service Manual TRSM0960
- Eaton Breakout Box with 74-Way Eaton Diagnostic Adapter - RR1029TR
- Digital Volt/Ohm Meter (DVOM)
Component Identification
 |
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 637 Troubleshooting
Set vehicle parking brake and chock wheels.
Record transmission fault codes, FMIs, occurrences, and timestamps from Service Activity Report created during the Diagnostic Procedure.
If Fault Code 637 FMI 0, 1, 3, 4, 5, 6, 8, 16, 18, 31 is Active or Inactive, Go to Step B
If Fault Code 637 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 637 FMI 7, 14, 15, 17 is Active or Inactive, Go to Step E
Key off.
Remove TCM from MTM with 20-Way TCM Vehicle Harness Connector and 20-Way TCM Body Harness Connector connected.
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.
Inspect TCM Seal, verify seal is properly installed and not damaged.
If contamination or damage is found, replace Transmission Control Module (TCM) and Mechatronic Transmission Module (MTM). Go to Step V
Note: MTM removal and installation requires transmission be removed from vehicle. Reference Endurant XD Service Manual TRSM0960, Transmission Removal Service Procedure.
If no contamination or damage is found, Go to Step C
Key off.
Connect Eaton Breakout Box with 74-Way Eaton Diagnostic Adapter to MTM side of 74-Way Transmission Harness Connector.
Measure resistance at Eaton Breakout Box between Pin 1 and Pin 2. Record reading in table.
Measure resistance at Eaton Breakout Box between Pin 1 and Ground (TCM mounting stud). Record reading in table.
Compare reading(s) in table.
If readings are in range, Go to Step D
If readings are out of range, replace Mechatronic Transmission Module (MTM). Go to Step V
Note: MTM removal and installation requires transmission be removed from vehicle. Reference Endurant XD Service Manual TRSM0960, Transmission Removal Service Procedure.
| Pins | Range | Reading(s) |
|---|---|---|
| 1 to 2 | 3.4–5.5 Ohms | |
| 1 to ground (TCM mounting stud) | Open Circuit (OL) |
Key off.
Remove Eaton Breakout Box 74-Way Eaton Diagnostic Adapter.
Reinstall TCM to MTM.
Reconnect all connectors and verify all components are properly installed.
Key on with engine off.
Connect ServiceRanger.
Retrieve and record transmission fault codes, FMIs, occurrences, and timestamps.
If Fault Code 637 FMI 0, 1, 3, 4, 5, 6, 8, 16, 18, 31 is Active, replace Transmission Control Module (TCM). Go to Step V
If Fault Code 637 FMI 0, 1, 3, 4, 5, 6, 8, 16, 18, 31 is Inactive, replace Mechatronic Transmission Module (MTM). Go to Step V
Note: MTM removal and installation requires transmission be removed from vehicle. Reference Endurant XD Service Manual TRSM0960, Transmission Removal Service Procedure.
Key off.
Remove MTM.
Note: MTM removal and installation requires transmission be removed from vehicle. Reference Endurant XD Service Manual TRSM0960, Transmission Removal Service Procedure.
Inspect Driven Gear 1st for excessive fore and aft movement.
Inspect Reverse Gear for excessive fore and aft movement.
If excessive gear movement is evident, inspect Main Shaft Assembly for cause and repair. Go to Step V
If no excessive gear movement is evident, Go to Step F
Inspect Rail D Sliding Clutch yoke slot for wear.
Shift Rail D Sliding Clutch to neutral position (if necessary).
Shift Rail D Sliding Clutch into Driven Gear 1st engagement position (fore).
Inspect Rail D Sliding Clutch clutching teeth for wear.
Return Rail D Sliding Clutch to neutral position.
Shift Rail D Sliding Clutch into Reverse Gear engagement position (aft).
Inspect Rail D Sliding Clutch clutching teeth for wear.
Return Rail D Sliding Clutch to neutral position.
If Rail D Sliding Clutch shifts into all three positions and no clutching teeth wear is present, replace Mechatronic Transmission Module (MTM). Go to Step V
If Rail D Sliding Clutch does not shift into all three positions or clutching teeth wear is present, replace Rail D Sliding Clutch, Driven Gear 1st, Reverse Gear, and Mechatronic Transmission Module (MTM). Go to Step V
Key off.
Reconnect all connectors and verify 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 vehicle operates properly, test complete.
If Fault Code 637 sets Active, Go to Step A
If a fault code other than 637 sets Active, troubleshoot per the Fault Code Isolation Procedure Index.