Fault Code 646: Rail E Fore Solenoid (A6) (TRTS0950)

Endurant HD

TRTS0950 EN-US

October 2024 - B

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 Mechatronic Transmission Module (MTM) is equipped with solenoids to direct pneumatic flow. The Rail E Aft Solenoid (REFS) is energized by the Transmission Control Module (TCM) to direct vehicle supplied air pressure to actuate the Rail E Sliding Clutch in the aft or rearward direction. The REFS is located in the MTM and connected to the TCM at the 74-Way Transmission Harness Connector.

Detection

The TCM monitors the REFS. 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 is greater than commanded current.

FMI 1 – Data Valid But Below Normal (Most Severe): REFS low side current is less than commanded current.

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

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

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

FMI 6 – Current Above Normal or Shorted Circuit: REFS commanded on and shorted to ground.

FMI 7 – Mechanical System Not Responding: One time during an ignition cycle, Rail E Position Sensor reported uncommanded movement fore, out of Low Range, and speed sensors confirmed the loss of Low Range engagement.

FMI 8 – Abnormal Frequency: REFS out of normal operating frequency.

FMI 12 – Bad Intelligent Device: REFS commanded on beyond expected duty cycle.

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

FMI 17 – Data Valid but Below Normal (Least Severe): Rail E Position Sensor reported uncommanded movement fore, out of Low Range, and speed sensors confirmed the loss of Low Range engagement.

FMI 18 – Data Valid but Below Normal (Moderately Severe): REFS commanded on below expected voltage.

Fallback

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

Amber warning lamp on
If vehicle is stationary and Rail E is not engaged in High Range or Neutral
- Rail E movement in the fore direction prohibited

FMI 7:

No degraded modes

FMI 17:

Amber warning lamp on
If vehicle is stationary in a non-neutral mode and engine is running
- Rail E engagement of Low Range prohibited

Conditions to Set Fault Code Inactive

FMI 0, 1, 6, 7, 8, 12, 16, 17, 18: Key cycle

FMI 3, 4, 5: REFS in range 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 HD Service Manual TRSM0950
Eaton Breakout Box with 74-Way Eaton Diagnostic Adapter - RR1029TR
Digital Volt/Ohm Meter (DVOM)
MTM Alignment Tool (RR1086TR-1)

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. Mechatronic Transmission Module (MTM)

_Graphics/LineArt/TRTS0950_FC275_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. Mechatronic Transmission Module (MTM)

Fault Code 646 Troubleshooting

Purpose:Check for active or inactive fault codes.

Set vehicle parking brake and chock wheels.
Key off.
Record the transmission fault codes, FMIs, occurrences, and timestamps from the 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 G

Purpose:Verify condition of 74-Way Transmission Harness Connector.

Key off.
Remove the TCM from the MTM with the 20-Way TCM Vehicle Harness Connector and 20-Way TCM Body Harness Connector connected.
Inspect the TCM side of the 74-Way Transmission Harness Connector, verify the connector is free from contamination and corrosion; the terminals are not bent, spread or loose; and there is no damage to the connector body.
Inspect the TCM Seal, verify the seal is properly installed and not damaged.

If contamination or damage is found to the TCM side of the 74-Way Transmission Harness Connector, replace the Transmission Control Module (TCM) and Mechatronic Transmission Module (MTM). 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 or damage is found, Go to Step C

Purpose:Identify MTM Type.

Key on with engine off.
Connect ServiceRanger.
Go To “Configuration”.
Select “Advanced”.
Note: If “Advanced” is not indicated, TCM software is unable to determine MTM Type. Go to Step 6.
Record “MTM Type” Current Value, go to Step 7.
Locate MTM part information tag and record MTM Part Number (Item 1) in table.
Compare MTM Part Number recorded in Step 6 with MTM Part Number in table to determine MTM Type.

If MTM Type is PS-393, Go to Step D

If MTM Type is PS-496, Go to Step E

MTM Part Number on tag

MTM Part Number	MTM Type
A-10000715	PS-393
A-10002594
A-10004202
A-10004231	PS-496
A-10004356
A-10004383

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

Key off.
Connect the Eaton Breakout Box with 74-Way Eaton Diagnostic Adapter to the MTM side of the 74-Way Transmission Harness Connector.
Measure resistance at the Eaton Breakout Box between Pin 30 and Pin 31. Record reading in table.
Measure resistance at the Eaton Breakout Box between Pin 31 and Ground (TCM mounting stud). Record reading in table.
Compare reading(s) in table.

If readings are in range, Go to Step F

If readings are out of range, replace Mechatronic Transmission Module (MTM). 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.

Pins	Range	Reading(s)
30 to 31	3.6–4.4 Ohms
31 to ground (TCM mounting stud)	Open Circuit (OL)

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

Key off.
Connect the Eaton Breakout Box with 74-Way Eaton Diagnostic Adapter to the MTM side of the 74-Way Transmission Harness Connector.
Measure resistance at the Eaton Breakout Box between Pin 38 and Pin 39. Record reading in table.
Measure resistance at the Eaton Breakout Box between Pin 38 and Ground (TCM mounting stud). Record reading in table.
Compare reading(s) in table.

If readings are in range, Go to Step F

If readings are out of range, replace Mechatronic Transmission Module (MTM). 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.

Pins	Range	Reading(s)
38 to 39	3.4–5.5 Ohms
38 to ground (TCM mounting stud)	Open Circuit (OL)

Purpose:Check for Active or Inactive fault codes.

Key off.
Remove the 74-Way Eaton Diagnostic Adapter.
Reinstall the TCM to the MTM.
Reconnect all connectors and verify that all components are properly installed.
Key on.
Connect ServiceRanger.
Retrieve and record the transmission fault codes, FMIs, occurrences, and timestamps.

If Fault Code 646 FMI 0, 1, 3, 4, 5, 6, 8, 16, 18 is Active, replace the Transmission Control Module (TCM). Go to Step V

If Fault Code 646 FMI 0, 1, 3, 4, 5, 6, 8, 16, 18 is Inactive, replace the Mechatronic Transmission Module (MTM). 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.

Purpose:Verify mechanical movement of the Rail E Range Synchronizer

Key off.
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.
Install the MTM Alignment Tool (RR1086TR-1) onto the main housing.
Note: Reference Appendix/Manually Actuate Rail E Procedure.
Using the Rail E Lever, move Rail E to neutral (if necessary).
Shift Rail E into the High Range (fore) engagement position and return to neutral.
Shift Rail E into the Low Range (aft) engagement position and return to neutral.

Contact Eaton Cummins Automated Transmission Technologies at 800-826-4357 for further diagnostic instructions. 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 646 sets Active during operation, Go to Step A

If a fault code other than 646 sets Active, troubleshoot per the Fault Code Isolation Procedure Index.