Cars are a complicated thing and often parts go bad without your even knowing where to start in order to fix them. That being said, when something like the ICP sensor goes out in your car, there are a few different things you should know about what it can do to the performance of your car. The ICP sensor, like many sensors in your car, can affect the overall performance of your car.
The first thing that many people ask when the ICP sensor goes out is, does this affect my fuel mileage. The first and foremost condition that is directly caused by a bad ICP sensor is of course revving and shutting off without warning. The ICP sensor does not necessarily affect the gas mileage but it can affect the overall running of your car or truck. In a diesel engine, the ICP sensor works as a moderator of sorts that insures the engine is running at maximum efficiency. ICP stands for Injection Control Pressure. This means that the sensor provides feedback and indicates the needed and existing injection pressure in the injectors.
Though it can have an adverse effect on fuel economy in a limited range, disconnecting a sensor or having a sensor that is not working properly does not mean that you will go from having a truck or car that gets 30 miles per gallon that plummets to 10 miles per gallon. Likely, the change will be small so you may not even notice that there has been a change in fuel economy. More likely, you will notice that the engine is not being controlled as specifically or as closely as it may have been in the past. This can be seen through revving and stopping that is directly related to the pressure that should be indicated by the faulty sensor.