Problems with the Crankshaft Position Sensor (CPS) on Mercedes-Benz cars are fairly common. If you have been experiencing stalling or no start conditions, a failed crankshaft position sensor is often the problem. Your CPS may have failed if the engine cranks but it will not start. At first, you may experience no start conditions intermittently. As the crankshaft position sensor fails completely, the car will no longer start or will die when you are driving. Starting problems are initially random, but more frequent when the engine is hot. Other symptoms of a failed crankshaft position sensor are poor acceleration, engine vibrations, poor throttle response, bad fuel economy, hesitation, engine stalls. The engine starts if you let it cool down. If you are stuck on a parking lot and the car will not start, let the car cool down at least 30 minutes and then try again.
How to replace the crankshaft position sensor on a Mercedes-Benz
In this repair guide, we will show you how to replace the CPS yourself. The crankshaft position on most Mercedes-Benz cars such as E320, C240, S430, S500 is located at the back of the engine by the flywheel housing, in front of the firewall. It monitors the engine crankshaft position and speed and is one of the most important input sensors that is used by the Engine Control Unit (ECU).
Here is a list of the tools that you will need to change the CPS on your Mercedes-Benz. We have provided links to Amazon products if you need any of these tools.
A new crankshaft position sensor can be ordered on Amazon for under $50. Make sure to enter the year and model of your Mercedes-Benz to get the correct fit.
Remove engine cover. Disconnect the two air tubes from the engine cover. Grab the engine cover and lift it up. There are no screws that hold the engine cover in place, only four clips.
Locate the crankshaft position sensor (CPS) on driver’s side, towards the rear of engine. Back of engine, near the firewall.
Unplug the electrical connector from the CPS sensor. Squeeze the connector and pull it away from the CPS sensor.
Remove bolt. Remove the crankshaft position sensor. You will have either an E8 or E10 bolt that holds the CPS sensor in place.
Install new sensor. Place the new sensor in the crankshaft position sensor hole and hand tighten the bolt. Once you can no longer hand tighten the bolt, use the 3/8 ratchet to tighten the bolt. Torque the bolt to about 10Nm. or 7 ft-lb if you have a 3/8 torque wrench.
Next push the electrical connector plug into the CPS end until you hear a click.
Reinstall the engine cover. Place the engine cover back on top of the engine. Make sure that the engine cover is not loose.
Symptoms of a defective crankshaft position sensor on a Mercedes-Benz
Engine Cranks but no Start, Dies, Stalls, or Backfires
A failed crankshaft position sensor can cause your engine to stall or not start at all. Your Mercedes-Benz may start and run for a short time, or until it gets warm and then it dies. The engine may crank, but it will not start. You may need to crank the engine longer in order to get it to start.
Failed crankshaft position sensor can also impact the idling, the acceleration, or even your transmission shifting. In some cases, it can cause your transmission to go into limp mode. You may also notice an increase in engine vibrations.
Check engine light
The check engine light is usually illuminated on your instrument cluster. You can easily use a $20 scanner to read the fault code which will tell you why the check engine light is on. When the CPS is malfunctioning, the engine control module will trigger a fault code if it does not receive any signal from the CPS.
Fault codes related to the crankshaft position sensor are:
- P0335 Crankshaft Postion Sensor A Circuit Malfunction
- P0336 Crankshaft Position Sensor A Circuit Range / Performance
- P0337 Crankshaft Position Sensor A Circuit Low Input
- P0338 Cranshaft Position Sensor A Circuit High Input
- P0339 Crankshaft Position Sensor A Circuit Intermittent
- P0385, P0386, P0387, P0388 P0389 are related to B Circuit.
- P1336 usually related to a wiring problem, air gap, flywheel ring gear damaged, CPS sensor.
Ignition Malfunction / Stall / No Start
If the crankshaft position sensor fails, it will not send information about the position of the crankshaft and speed of the engine RPMs to the ECU. As a result, the ECU doesn’t know when to send the spark plugs and how to adjust the fuel mixture. This can cause your car to stall or hesitate to start. If your car has been hesitating to start then you should have the crankshaft position sensor inspected.
Crankshaft Position Sensor Replacement Cost?
At an auto mechanic or dealership
While the prices vary based on your location the average cost of replacing the crankshaft position sensor at an auto mechanic or the Mercedes-Benz dealership vary between $250 and $400.
The crankshaft position sensor cost between $100 and $150 at the dealership, that’s for the parts only.
Do It Yourself Cost
If you decide to replace the crankshaft position sensor yourself, you can get the job done for around $80 USD. We will show you how you can do this, by buying the sensor online and the tools that you will need to complete this repair.
Frequently Asked Questions
Where is the Crankshaft Position Sensor Location?
The CPS sensor is located on the back of the engine, near the firewall.
Mercedes Crankshaft Position sensor replacement cost?
DIY cost is around $50, if you have to take it to a shop you will be spending between $300-$400.
How long does it take to replace the crankshaft position sensor?
It will take you one to two hours if you are replacing the sensor for the first time.
How difficult is it to replace the crankshaft position sensor?
The sensor is held in place with one bolt. It is easy to replace the sensor, the hardest part is accessing it, as there typically isn’t enough room for your hands.
In some models it is easier than others, all depends on how close the engine is to the firewall.
Where can I buy a crank shaft position sensor?
You can find a crankshaft position sensor for your Mercedes-Benz on Amazon. Even the OEM brand can be purchased online. See here:
VIDEO How to replace crankshaft position sensor on a Mercedes-Benz engine.
Applicable Part Numbers and Models
Manufacturer Part Number: 003 153 27 28 ; 003 153 2828 ; A0031532728
Interchange Part Number: 0031532728 ; 0031532828 ; A0031532828
Other Part Number: 026 121 01 70 ; 0261210170
Replacement P/N: 003 153 27 28 / 003 153 2828 / A0031532728;
Replacement P/N: 0031532728 / 0031532828 / A0031532828 / 026 121 01 70 / 0261210170 / PC497;
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