2004 BMW 330Ci Camshaft Position Sensor Replacement Cost

As the camshaft spins, the camshaft position sensor magnetically reads its position. The sensor continually sends this information to the engine's computer for comparison with data from the crankshaft position sensor. When the two signals reach the computer, they must match. If they don't, the computer will believe that an engine timing problem is occurring, and adjust settings in order to protect the engine.

When the computer senses the engine is out of time, it will turn on the check engine light. The engine may stall or even just fail to start. If the engine runs, it will run poorly and get bad fuel mileage. 

It's a bad idea to drive a vehicle with a failed camshaft or crankshaft position sensor — in fact, it's usually impossible. 

Using a scan tool, a mechanic can read where the computer believes the crankshaft and camshaft are, and compare that information to their actual position. If the reading is incorrect, the position sensor will be tested, and replaced if necessary.

Replacement of the camshaft position sensor is completed by disconnecting the electrical connector or connectors and unscrewing the sensor. If required, sealant will be applied before inserting the new sensor into the engine. Finally the electrical connector is connected, and the vehicle is tested to confirm the repair. There are two common locations for the camshaft position sensor: inside the timing cover and near or on the engine's valve cover.

After replacing the camshaft position sensor, the engine's computer will need to be recalibrated.

When replacing the camshaft position sensor, make sure there are no obvious oil or coolant leaks that could ruin the new sensor. High-quality sensors — preferably OEM parts — should be used, as lesser products will likely lead to a repeated repair. Also, the vehicle's timing belt should be inspected at this time. If the timing belt or timing chain has failed, it will need to be replaced.

Diagnosis is key when it comes to sensor replacement, as other problems could cause the same symptoms. If the issue can't be diagnosed at home, a professional technician should be trusted with the issue.