CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 241

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


Fault Code: 241
PID: P084
SPN: 84
FMI: 2/2
LAMP: Amber

Wheel-Based Vehicle Speed – Data Erratic, Intermittent or Incorrect. The ECM lost the vehicle speed signal.

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

ISM and ISX – Vehicle Speed Sensor Circuit

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 electronic 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 troubleshooting and repair manual.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the vehicle is in motion.

Conditions for Setting the Fault Codes

The ECM detects a loss of vehicle speed when other engine operating conditions indicate that the vehicle should be in motion.

Action Taken When the Fault Code is Active

  • The ECM illuminates the amber CHECK ENGINE light 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

  • The ECM detects a valid engine speed signal from the vehicle speed sensor.
  • The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

Shop Talk

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

There are multiple types of vehicle speed sensors. Various types include magnetic pickup, data link, digital, and tachograph. Refer to 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 vehicle speed signal greater than zero.

Since the vehicle speed sensor is an OEM installed component, this troubleshooting procedure will not catch all failures 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, please refer to the OEM troubleshooting and repair manual.

Refer to Troubleshooting Fault Code t05-241

Last Modified:  09-Jul-2010