Cummins ISB4.5 CM2150 Fault Code: 242 PID: SPN: 84 FMI: 10 Wheel-Based Vehicle Speed Sensor Circuit Tampering Has Been Detected – Abnormal Rate of Change.

Circuit Description
The vehicle speed sensor senses the speed of the tailshaft gear on the vehicle 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.

Conditions for Running the Diagnostics
-The adjustable parameter “VSS Anti-Tampering” must be enabled.
-This diagnostic runs continuously when the vehicle is in motion, if the feature is enabled.

Conditions for Setting the Fault Codes
The ECM detects a tampering event of the vehicle speed signal.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE light and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
-The engine speed operating range is limited to the adjustable parameter “Maximum Engine Speed without VSS”.
-Cruise Control, Gear-Down Protection, and Road Speed Governor features will be disabled.

Conditions for Clearing the Fault Code
-The ECM detects a valid engine speed signal from the vehicle speed sensor.
-The keyswitch must be turned ON, and the vehicle speed and engine speed must be zero for 30 seconds.
-The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.
-The ECM will turn off the malfunction indicator lamp (MIL) after three consecutive ignition cycles that the diagnostic runs and passes.

Shop Talk
Verify the feature settings for the vehicle speed sensor anti-tampering (Fault Code 242), application type and automatic transmission are set correctly. If any of these are set incorrectly for the specific vehicle and application, Fault Code 242 could occur erroneously.

Driving techniques such as driving for extended periods of time in lower gears can log Fault Code 242. Fault Code 242 can be logged if the driver attempts to defeat the road speed governor by repeatedly cycling the keyswitch.

When the speed signal has been restored, the fault code will go inactive, once the keyswitch is on for 30 seconds and the ECM senses zero vehicle and engine speed.