The crankshaft position sensor is an essential measuring tool inside your Mercedes and a necessity in all modern combustion engines. Its role is to monitor the position and the rotational speed of the crankshaft. It will provide this information to your ECU, or engine control unit, which is your Mercedes’ main onboard computer. This information allows the ECU to make necessary adjustments to the crankshaft to achieve optimal operating conditions.
The information of crankshaft speed and position are some of the most important pieces of information that are used in all engine management calculations, which means that if the crankshaft position sensor fails, most engines simply won’t run.
Luckily for drivers, when the crankshaft position sensor starts to fail, some warning signs and symptoms will begin to appear when operating your Mercedes. As the crankshaft position sensor is so important, let’s learn more about its function as well as how to know when problems are occuring.
A Closer Look at the Crankshaft Position Sensor
The crankshaft position sensor is found near the flywheel ring gear. There are 2 designs of sensor which your Mercedes may use: an inductive sensor or a hall generator. The sensor works by using the rotational movement of the ring gear, which alters a magnetic field. The magnetic field will generate a variety of voltage signals inside the sensor which are transmitted to the sensor control unit. The sensor control unit is able to convert this information into usable data, which allows it to calculate the crankshafts’ speed and position. It will then pass on to the ECU.
Common Causes of Faults in the Crankshaft Position Sensor
Crankshaft position sensor failures most commonly occur because of any of the following:
- internal short circuits
- damage or breaks in wiring
- short circuit of wiring
- mechanical damage to the encoder wheel
- soiling most commonly caused by metal abrasion
Signs and Symptoms that your Crankshaft Position Sensor is Faulty
The following signs and symptoms can all indicate other issues within your Mercedes, such as fuel system issues. However, once these culprits have been ruled out, if you’re faced with any of the symptoms listed below, you will need to turn your attention to the crankshaft position sensor.
Your Mercedes Struggles to Start
A faulty crankshaft position sensor will almost always result in trouble starting your car. As the sensor is needed to measure the position and speed of the crankshaft, which is essential to engine function and timing, when the important information isn’t being relayed, the chances of starting your Mercedes successfully becomes much less likely. Eventually, if the issue is allowed to become worse, your Mercedes will end up not being able to start at all.
Your Mercedes will Start to Stall Intermittently
A failing crankshaft position sensor will also result in your Mercedes stalling intermittently. This can be caused by faults in the sensor’s wiring and not actually an issue with the sensor itself. This can cause a spotty connection, meaning that the sensor’s signals only make it to the ECU some of the time, despite the unit itself functioning correctly. This will result in your Mercedes driving normally and then suddenly stalling when the connection is lost. Of course, it goes without saying that this type of issue needs to be dealt with immediately, as sudden and unpredictable stalling will make your car a danger to you and other motorists due to the risk of collisions.
Illumination of Check Engine Light
The illumination of engine management light (EML) or check engine light can occur for a variety of reasons, but it is important to never skip over checking the status of your crankshaft position sensor. When issues are detected by the ECU regarding the crankshaft position sensor’s signal, it will alert the driver by illuminating the EML. It will also send the relevant fault codes to the OBD unit, which can help your mechanical technician diagnose the issue for proper repairs.
Master Mechanics Auto Repair
If your crankshaft position sensor is beginning to fail, 
come into Master Mechanics Auto Repair of Battle Creek, Portage, Kalamazoo, MI. Let our experts inspect, diagnose, and repair your Mercedes Benz and return it to you in its top-functioning condition. Call us today to schedule an appointment.
* Mercedes-Benz image credit goes to: y_carfan.