PACCAR PX-9 CM2350 (2013-17) Fault Code:241 PID:84 SPN:84 FMI:2 Wheel-Based Vehicle Speed – Data Erratic, Intermittent, or Incorrect

Reason:
Wheel-Based Vehicle Speed – Data Erratic, Intermittent, or Incorrect. 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:
1) The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.
2) The engine speed operating range is limited to the adjustable parameter “Maximum Engine Speed without VSS”.
3) ECM powerdown will be delayed for 60 seconds after key OFF.

Conditions for Clearing the Fault Code:
1) To validate the repair, start the engine and move the vehicle so the ECM can read a vehicle speed. The vehicle may need to be driven for up to 15 minutes to get the diagnostic to run and the fault to go inactive.
2) The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
3) The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
4) For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
5) The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

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.

A damaged vehicle speed sensor or debris on the end of the sensor could cause the fault to become active. Incorrect INSITE™ electronic service tool feature and parameter settings (gear ratio, tire size, rear axle ratio, etc) will also cause the fault to become active. Feature and parameter settings under Transmission Setup and Vehicle Speed source need to be verified with the vehicle components.

NOTE: If the power is removed from the ECM within 60 seconds of key OFF and before the ECM has powered down, Fault Code 1117 may become active

Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM For intermittent power supply and datalink communication issues with Aftertreatment Components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing or intermittent connections.

Possible Causes:
1) Faulty OEM harness
2) Faulty ECM
3) Damaged OEM harness connector pins at the ECM
4) Open circuit in the OEM harness
5) Short circuit to ground in the OEM harness
6) Pin-to-pin short circuit in the OEM harness
7) Gear slipping on the shaft
8) Inactive fault codes