Types of Engine Input Sensors
There are many types of input sensors. The sensor above is a permanent magnet sensor. Engine manufacturers use crankshaft and camshaft position sensors as position sensors. All distributorless (EI) electronic ignition systems require a crankshaft position sensor. Most engines 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.
Engine coolant temperature sensors or (ECT) sensors are variable resistors that use resistance to alter 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 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. It's a variable resistor used to control voltage in a circuit. The TP sensor detects the engine's load. The PCM and the TCM share the signal. This sensor's input signal, along with the vehicle speed sensor, is used by the TCM to provide optimal shift timing.
The oil pressure switch sends a signal directly to the driver's instrument panel or 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.