SPN 84 - FMI 2 (Fault Code 241)

Wheel-Based Vehicle Speed - Data Erratic, Intermittent, or Incorrect

Vehicle Speed Sensor Circuit

Fault Code: 241
PID(P), SID(S): P84
SPN: 84
FMI: 2/2
Lamp: Amber

REASON: The ECM lost the vehicle speed signal or is reading an erratic value.

EFFECT: Engine speed limited to Maximum Engine Speed without VSS parameter value. Cruise
Control, Gear-Down Protection, and Road Speed Governor will not work.

Circuit Description:
The vehicle speed sensor senses the speed of the tailshaft gear on the vehicle's transmission. This speed signal is then transmitted to the engine control module (ECM) and converted into a vehicle speed.

Component Location:
The vehicle speed sensor is located in the rear of the vehicle transmission. Refer to the OEM service manual for location.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the vehicle is in motion, if the feature is enabled.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected a loss of vehicle speed when other engine operating conditions indicated that the vehicle should be in motion. This fault code can also become active if the calculated gear ratio and actual gear ratio do not agree while the vehicle is in motion.

Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.
-The engine speed operating range is limited to the adjustable parameter "Maximum Engine Speed without VSS".

Conditions for Clearing the Fault Code:
• To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
• The fault code status displayed by the recommended Cummins® electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
• The "Reset All Faults" command in the recommended Cummins® electronic service tool or equivalent can be used to clear active and inactive faults.

Shop Talk:
There are multiple types of vehicle speed sensors. Various types include magnetic pickup, data link, digital, and tachograph. Contact the OEM for the specific type installed on the vehicle.

This fault is set active when the ECM loses a vehicle speed signal when other engine conditions indicate the vehicle is moving. The fault can also become active if there is a series of clutch, service brake or throttle movements with no vehicle movement. The fault is set inactive when the ECM receives a valid vehicle speed signal.

Since the vehicle speed sensor is an OEM installed component, this troubleshooting procedure will not cover all malfunctions of the circuit due to components not under Cummins® Inc. control. Sensor resistance values, data link speed sensors and tachographs are not fully covered under this procedure. For more information on those components, refer to the OEM service manual.

Read More:
SPN 647 - FMI 4 (Fault Code 245)
SPN 84 - FMI 10 (Fault Code 242)


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