The purpose of the camshaft sensor in a Volvo S40 is to record the rate of speed and the revolutions of the crankshaft. This helps fuel economy and engine timing. The sensor sends information to the S40's computer, and the computer makes changes to improve the fuel economy. The sensor also helps determine if there are problems that need to be addressed. Locating and replacing a camshaft sensor will help save you money for many miles to come.
Park the S40 on a level surface. Set the parking brake. Lift the bonnet and prop it open to access the engine compartment. The raised hood will help to provide needed light.
Place a jack under the crossmember and raise the car high enough to place jack stands under the crossmember. Lower the car onto the jack stands.
Crawl under the car to access the side of the engine. Locate the main pulley at the bottom centre of the engine. Use a flashlight for visibility. This will be largest pulley among the pulleys bolted to the engine.
Locate the camshaft sensor above the main pulley. The sensor is round, with a wiring harness plugged into it. The sensor is bolted to the engine by the cylinder heads.
You can see the sensor more easily from under the vehicle.