Modern cars have sensors keeping tabs on all areas of their function and performance. These sensors have allowed engines to become more efficient and for automakers to reduce the amount of harmful emissions caused by vehicles. Sensors provide data to engine computers, which can adjust fuel delivery and spark timing for optimum performance. One of the most crucial sensors is the motor position sensor, which tells the car's electronics what position the motor is in, and therefore if it is running correctly. Read on to learn more about this sensor, what it does, where it is, and what repairs to expect if it fails.
A motor position sensor, also commonly referred to as a crank position sensor (CPS), is a device used to monitor the speed and position of the crankshaft in the engine. It is used with engine computers (ECM) to control ignition timing and engine operating parameters. It plays a particularly important role in fuel injection by allowing the engine's computer to monitor the position of each cylinder. The sensor is also a primary source of information about the engine's speed, measured in revolutions per minute (RPM).
Different automakers place them in different locations, but generally the sensor will be mounted somewhere along the crankshaft. The sensor works by detecting a magnetic pulse as the crankshaft rotates past it. The ECM is thereby able to calculate the position of each cylinder and the engine's RPM. One common location is mounting it next to the flywheel. Some automakers place the CPS on the camshaft, though usually it has a separate sensor. It can also be located on a cylinder head, and detect the movement of one the cylinders.