The camshaft sensor sets the cylinder firing sequence and coordinates the fuel injector and coil firing cycles. It works together with the crankshaft position sensor to control engine timing and signals the correct RPM to determine the engine speed.
The crankshaft sensor signals the fuel injection computer or the ignition control when the cylinders are firing. This causes the ignition coil to provide a spark and the injector to inject fuel into each cylinder at the right time.
If either sensor isn't working correctly, the car will run rough and the engine will be less efficient. In later car models, the car's computer can usually keep the vehicle running, but the engine warning light on the dashboard goes on to warn the driver.
If the engine cylinders are too far out of sync, the computer will shut the car off or prevent it from starting. An overheated engine will sometimes cause the sensors to fail.
The camshaft sensor is usually located in the cylinder head of the engine. Part of it is shaped like a cylinder shaft and fits into the head. The crankshaft sensor is typically in the timing cover or on the side of the engine block. It also has a cylindrical section that fits into the block.
Sometimes the words camshaft sensor and crankshaft sensor are used interchangeably. Depending on the make and model, a vehicle could have one or both sensors, or a different type of timing regulator.