Fault Code 370: Countershaft Speed (TRTS0960)

Endurant XD

TRTS0960 EN-US

December 2024 - D

Fault Code 370: Countershaft Speed

J1939: SA 3 SPN 160 FMI 2, 3, 4, 5, 6, 8, 9, 10, 14, 20, 21

Overview

The Endurant XD Series transmissions are equipped with speed sensors to monitor Input, Countershaft and Output speeds. The speed sensors provide rotational speed inputs to the Transmission Control Module (TCM) for the purpose of verifying clutch engagement, making shift decisions, and confirming gear engagements. The Countershaft Speed Sensor measures the rotational speed of the Countershaft. The Input and Countershaft speed sensors are located in the Mechatronic Transmission Module (MTM) and are connected to the Transmission Control Module (TCM) at the 74-Way Transmission Harness Connector.

Detection

The TCM monitors the Countershaft Speed Sensor signal. If a system failure is detected, the fault is set Active.

Conditions to Set Fault Code Active

FMI 2 – Data Erratic: Countershaft Speed Sensor signal out of range for 5 seconds.

FMI 3 – Voltage Above Normal or Shorted High: Countershaft Speed Sensor circuit shorted to power for 5 seconds.

FMI 4 – Voltage Below Normal or Shorted Low: Countershaft Speed Sensor circuit shorted to ground for 5 seconds.

FMI 5 – Current Below Normal or Open Circuit: Countershaft Speed Sensor circuit open or shorted to power for 5 seconds.

FMI 6 - Current Above Normal or Shorted Circuit: Countershaft Speed Sensor circuit supply voltage out of normal operating range (4.75V to 5.25V) for 5 seconds.

FMI 8 – Abnormal Frequency: Countershaft Speed Sensor signal frequency out of range for 5 seconds.

FMI 9 – Abnormal Update Rate: Countershaft Speed Sensor speed direction unknown for 5 seconds.

FMI 10 – Abnormal Rate of Change: Countershaft Speed Sensor signal rate of change exceeded for 2 seconds.

FMI 14 – Special Instructions: Countershaft Speed value out of range (near 0 RPM) when compared to calculated countershaft speeds based on known Input speed, Output speed and gear ratio, for 5 seconds.

FMI 20 – Data Drifted High: Countershaft Speed value greater than expected when compared to calculated countershaft speeds based on known Input speed, Output speed and gear ratio, for 2 seconds.

FMI 21 – Data Drifted Low: Countershaft Speed value less than expected when compared to calculated countershaft speeds based on known Input speed, Output speed and gear ratio, for 2 seconds.

Fallback

FMI 2, 3, 4, 5, 6, 8, 9, 10, 14, 20, 21:

Amber warning lamp on
Inertia Brake activation prohibited
If Fault Codes 350 and 375 are both Active and vehicle is moving
- Red stop lamp on
- Urge to Move and Creep Mode prohibited
- Inertia Brake activation prohibited
- Non-Neutral modes prohibited
- PTO Mode prohibited

Conditions to Set Fault Code Inactive

FMI 2: Countershaft Speed Sensor signal in range for 10 seconds.

FMI 3: Countershaft Speed Sensor circuit not shorted to power for 10 seconds.

FMI 4: Countershaft Speed Sensor circuit not shorted to ground for 10 seconds.

FMI 5: Countershaft Speed Sensor circuit not open or shorted to power for 10 seconds.

FMI 6: Countershaft Speed Sensor circuit supply voltage between 4.75V and 5.25V for 10 seconds.

FMI 8: Countershaft Speed Sensor signal frequency in range for 10 seconds.

FMI 9: Countershaft Speed Sensor speed direction known for 10 seconds.

FMI 10: Countershaft Speed Sensor signal rate of change in range for 10 seconds.

FMI 14, 20, 21: Countershaft Speed Sensor signal matches calculated countershaft speeds for 10 seconds.

Possible Causes

FMI 2, 14, 20, 21:

MTM - Countershaft Speed Sensor
- Internal failure
- Damaged
Internal Transmission
- Mechanical failure
TCM
- Software issue
- Internal failure

FMI 3:

TCM
- Internal failure

FMI 4, 5, 6, 8, 9, 10:

MTM - Countershaft Speed Sensor
- Internal failure
- Damaged
MTM - Countershaft Speed Sensor Harness
- Wiring shorted to power, shorted to ground or open
MTM - Transmission Harness
- Wiring shorted to power, shorted to ground or open
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)

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)

_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 370 Troubleshooting

Purpose: Check for active or inactive fault codes.

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 370 FMI 3 is Active or Inactive, Go to Step H

If Fault Code 370 FMI 4, 5, 6, 8, 9, 10 is Active or Inactive, Go to Step B

If Fault Code 370 FMI 2, 14, 20, 21 is Active or Inactive, Go to Step D

Purpose: Verify condition of TCM 74-Way Connector.

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

Purpose: Verify Countershaft Speed Sensor power supply at TCM.

Key off.
Connect Eaton Breakout Box with 74-Way Eaton Diagnostic Adapter to TCM 74-Way Connector.
Key on.
Measure voltage at Eaton Breakout Box between Pin 32 and Pin 42. Record reading in table.
Compare reading(s) in table.

If readings are in 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.

If readings are out of range, replace Transmission Control Module (TCM). Go to Step V

Ignition State	Pins	Range	Reading(s)
Key on	32 to 42	4.75–5.25 V

Purpose:Verify condition of TCM 74-Way Connector.

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 E

Purpose:Verify Countershaft Speed Sensor power supply at TCM.

Key off.
Connect Eaton Breakout Box with 74-Way Eaton Diagnostic Adapter to TCM 74-Way Connector.
Key on.
Measure voltage at Eaton Breakout Box between Pin 32 and Pin 42. 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 Transmission Control Module (TCM). Go to Step V

Ignition State	Pins	Range	Reading(s)
Key on	32 to 42	4.75–5.25 V

Purpose:Verify mechanical condition of the lower countershaft.

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 the lower countershaft Splitter Driven Gear for missing teeth and excessive movement.

If no missing teeth or no excessive movement evident, replace Mechatronic Transmission Module (MTM). Go to Step V

If missing teeth and/or excessive movement evident, identify cause for missing teeth and/or excessive movement and repair. Go to Step G

Purpose:Verify condition of the Countershaft Speed Sensor.

Inspect the Countershaft Speed Sensor in the MTM for damage.

If no Countershaft Speed Sensor damage is evident, Go to Step V

If Countershaft Speed Sensor damage is evident, Replace the Mechatronic Transmission Module (MTM). Go to Step V

Purpose: Check for active or inactive fault codes.

Confirm a Service Activity Report was downloaded and sent to Eaton.
Retrieve and record the transmission fault codes and FMI’s, and their occurrences and timestamps.

If Fault Code 370 FMI is Active or Inactive, replace Transmission Control Module (TCM). Go to Step V

Purpose:Verify repair.

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 370 sets Active, contact Eaton Cummins Automated Transmission Technologies at +1 800-826-4357 for further diagnostic instructions.

If a fault code other than 370 sets Active, go to Fault Code Isolation Procedure Index.