Types of Engine Input Sensors
There are many types of input sensors. The sensor above is a permanent magnet sensor. Crankshaft and camshaft position sensors are used by engine manufacturers as position sensors. Most cars will have either a hall-effect or a magnetic impulse triggering system. A permanent magnet crankshaft position sensor is located behind the harmonic balancer or directly on the engine block. All distributorless (EI) electronic ignition systems require a crankshaft position sensor.
Engine coolant temperature sensors or ECT sensors are variable resisters that use resistance to change a 5 volt reference signal from the PCM. The sensor's signal changes according to the engine's coolant temperature. It’s a vital component for maintaining an engine’s normal operating temperature. Located in the coolant stream, usually on or around the thermostat housing, its job is to constantly sense the temperature of the engine’s coolant.
The Throttle Position (TP) sensor is located on the throttle body of a fuel injected engine. This type of sensor is known as a potentiometer. A variable resister used to control voltage in a circuit. The TP sensor is used to detect engine load. Its output is shared by the PCM and the TCM. This sensor's input signal along with the vehicle speed sensor are used by the TCM to provide optimal shift timing.
The oil pressure switch sends a signal directly to the driver’s instrument panel or to the engine control module. It indicates if the engine’s oil pressure has fallen below a critical level of around 3-10 psi, depending on the engine. Gauge sending units are often variable resistors. The oil pressure sending unit above is a simple pressure switch. The switch can be normally open or normally closed. They are usually normally closed switches; this is why the oil pressure warning light illuminates when the engine is first started and goes out after the oil pressure rises.