Description:
This tamper -resistant feature is a programmed engine RPM limit that the engine will not exceed if the ECM should lose the vehicle speed signal. In other words, if the vehicle speed signal is lost the truck will not exceed the Vehicle Speed Limit (VSL). The VSL Protection parameter should be set high enough that the vehicle can limp home, but low enough that it will not be capable of exceeding the VSL.
Available:
All electronically controlled on-highway engines covered in this handbook
Range:
Advantages:
The tamper resistance feature helps deter those who may be tempted to try and circumvent the vehicle speed signal. If the ECM were to lose the vehicle speed signal for any reason, the engine rpm would be limited to the programmed RPM value of the VSL Protection parameter.
Disadvantages:
None
Recommendations:
Caterpillar recommends electronic engines be protected by setting this feature to an RPM value
equal to:
where;
VSL = Vehicle Speed Limit
Ra = Rear Axle Ratio
Rt = Transmission Ratio in the highest gear
M = Tire revolutions per mile