Fault Code 171: Engine Speed
J1939: SA 3 SPN 190 FMI 9, 13, 19
Overview
The Transmission Control Module (TCM)) receives the vehicle’s Engine Speed message over the Primary Data Link and Engine Speed Sensor #2 message over the Secondary Data Link. The TCM uses the Engine Speed as the primary engine speed message during normal transmission operation. If Engine Speed becomes unavailable, the Engine Speed Sensor #2 message allows the transmission to operate in a degraded mode.
Detection
The TCM monitors the Engine Speed message. If the message is not received or invalid, the TCM sets the fault code active.
Conditions to Set Fault Code Active
FMI 9 - Abnormal Update Rate: Engine Speed message not received for 5 seconds.
FMI 13 – Out Of Calibration: Engine Speed message not available for 5 seconds.
FMI 19 – Received Network Data In Error: Engine Speed messages invalid for 5 seconds.
Fallback
All FMIs:
- Amber warning lamp on
- PTO Mode prohibited
- If the vehicle is moving:
- Lowest available start gear only
- Urge to Move and Creep Modes prohibited
Note: Engine fallback modes will vary.
Conditions to Set Fault Code Inactive
All FMIs: Engine Speed signal received and valid for 10 seconds.
Possible Causes
All FMIs:
Vehicle Components
- Module(s)
- Engine speed sensor
- J1939 Data link
Note: Refer to OEM or engine manufacture for troubleshooting a failed system.
Additional Tools
- None
Fault Code 171 Troubleshooting
Set vehicle parking brake and chock wheels.
Record the transmission fault codes, FMIs, occurrences, and timestamps from the Service Activity Report created during the Diagnostic Procedure.
If Fault Code 171 is Inactive and there are other Active vehicle or transmission fault codes, troubleshoot all Active fault codes. Go to Step V
If Fault Code 171 FMI 13 is Active, refer to OEM and enable vehicle Engine speed SPN 190 signal message. Go to Step V
If Fault Code 171 FMI 13 is Inactive, Go to Step V
If Fault Code 171 FMI 9 or 19 is Active or Inactive, Go to Step B
Key on with engine on at idle.
Connect ServiceRanger.
Go to “Data Monitor”.
Select “Speed”.
Select “Engine speed”.
Select all of the “- 190” SPN sources.
Note: Not all sources will indicate a value.
Monitor vehicle tachometer and record engine idle RPM value in table.
Monitor ServiceRanger and record “Engine speed” rpm value in table.
Compare reading(s) in table.
If readings are out of range, refer to OEM guidelines for repair or replacement of the Engine speed signal message. Go to Step V
If readings are in range, no fault was found. The intermittent nature of the fault makes it likely that the problem is in the Engine speed signal message. Contact OEM for further diagnostic instructions. Go to Step V
| Engine Speed Signal Source | Range | Reading(s) |
|---|---|---|
| Vehicle Tachometer | Idle RPM | |
| 190 - Engine Speed | Within 150 RPM of Engine Idle |
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 171 sets Active during operation, Go to Step A
If a fault code other than 171 sets Active, troubleshoot per Fault Code Isolation Procedure Index.