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 from a vehicle Electronic Control Unit (ECU) over the Primary Data Link (J1939A). This information is used to determine transmission operation.
The TCM also receives the Engine Speed message over the Secondary Data Link (J1939B). The Secondary Data Link is used in the event that the Primary Data Link is inoperative and allows the transmission to operate in a degraded mode.
The Primary Data Link (J1939A) is connected to the TCM at the 20-Way TCM Vehicle Harness Connector. The Secondary Data Link (J1939B) is connected to the TCM at the 20-Way TCM Body Harness Connector.
Detection
The TCM monitors Engine Speed messages on the Primary Data Link (J1939A). If messages are not received or are invalid, the fault is set 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
FMI 9, 13, 19:
- Amber warning lamp on
- Coast Mode and Neutral Coast prohibited
- Urge to Move and Creep Mode prohibited
- Inertia Brake activation prohibited
- Upshifts prohibited
- Clutch engagements prohibited
- Non-Neutral modes prohibited
- PTO mode prohibited
- Hill Start Aid prohibited
- If vehicle is moving:
- Red stop lamp on
Note: Vehicle may have additional fallback modes. Refer to OEM.
Conditions to Set Fault Code Inactive
FMI 9, 13, 19: Engine Speed messages received and valid for 10 seconds.
Possible Causes
FMI 9, 13, 19:
- Vehicle Components
- Engine Speed message not enabled on Primary Data Link (J1939A)
- 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.
Additional Tools
- None
Fault Code 171 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 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 9, 19 is Active or Inactive, Go to Step B
If Fault Code 171 FMI 13 is Active, refer to OEM and enable vehicle Engine Speed message (SPN 190).Go to Step V
If Fault Code 171 FMI 13 is Inactive, Go to Step V
Key on with engine on at idle.
Connect ServiceRanger.
Go to “Data Monitor”.
Select “Speed”.
Select “Engine speed”.
Select all “- 190” SPN sources.
Note: Not all sources will indicate a value.
Monitor 190 - Engine speed value. Record reading in table.
Monitor vehicle tachometer engine idle RPM value. Recording reading in table.
Compare reading(s) in table.
If readings are out of range, refer to OEM guidelines for repair of the vehicle Engine Speed message (SPN 190) on Primary Data Link (1939A). Go to Step V
If readings are in range and no fault was found, the intermittent nature of the fault makes it likely that the problem is in the vehicle Engine Speed message (SPN 190) on Primary Data Link (J1939A). 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 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 171 sets Active, Go to Step A
If a fault code other than 171 sets Active, troubleshoot per Fault Code Isolation Procedure Index.