Fault Code 194: Rear Axle Left Wheel Speed
J1939: SA 3 SPN 1594 FMI 9, 13, 19
Overview
The Transmission Control Module (TCM) receives the vehicle’s Rear Axle Left Wheel Speed message from a vehicle Electronic Control Unit (ECU) over the Primary Data Link (J1939A). This message is used by the TCM to maintain transmission operation in the event the transmission output shaft sensor fails.
Detection
The TCM monitors Rear Axle Left Wheel Speed messages. If messages are not received or are invalid, the fault is set Active.
Conditions to Set Fault Code Active
FMI 9 - Abnormal Update Rate: Rear Axle Left Wheel Speed message not received for 5 seconds.
FMI 13 – Out of Calibration: Rear Axle Left Wheel Speed message not available for 5 seconds.
FMI 19 – Received Network Data in Error: Rear Axle Left Wheel Speed messages invalid for 5 seconds.
Fallback
FMI 9, 13, 19:
- Amber warning lamp on
- No degraded modes
Note: Vehicle may have additional fallback modes. Refer to OEM.
Conditions to Set Fault Code Inactive
FMI 9, 13, 19: Rear Axle Left Wheel Speed messages available and valid for 10 seconds.
Possible Causes
FMI 9, 13, 19:
- Vehicle Components
- Rear Axle Left Wheel Speed message not enabled
- Other vehicle ECU(s) faulted
- Vehicle Harness - Primary Data Link (J1939A)
- Wiring shorted to power, shorted to ground or open
- Terminals bent, spread, corroded, or loose
Note: Refer to OEM for troubleshooting a failed system.
Fault Code 194 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 194 is Inactive and there are other Active vehicle or transmission fault codes, troubleshoot all Active fault codes. Go to Step V
If Fault Code 194 FMI 9, 19 is Active or Inactive, refer to OEM guidelines for repair of the vehicle Rear Axle Left Wheel Speed message (SPN 1594). Go to Step V
If Fault Code 194 FMI 13 is Active, refer to OEM and enable vehicle Rear Axle Left Wheel Speed message (SPN 1594). Go to Step V
If Fault Code 194 FMI 13 is Inactive, 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 194 sets Active, Go to Step A
If a fault code other than 194 sets Active, troubleshoot per Fault Code Isolation Procedure Index.