Crankshaft position sensor

Reference: W220 Wiki Section WIS 05 Engine Timing

Description

Crankshaft position sensor (CPS).

Sensor in engine crosscut.

The crankshaft position sensor (CPS) is located on driver’s side, towards the rear of engine. Back of engine, near 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). 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.

Problems with the Crankshaft Position Sensor 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.

Symptoms of fault:

• The engine may crank, but it will not start (starting problems are initially random, but more frequent when the engine is hot).
• The engine cranks longer in order to get it to start.
• Car runs for a short time, or until it gets warm and then it dies.
• Poor acceleration, engine vibrations, poor throttle response, bad fuel economy.
• Impact on transmission shifting. In some cases, it can cause the transmission to go into limp mode.

Hint: 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. What happens is when the car gets hot, the sensor's resistance goes open circuit, thus the car dies. Now since the sensor is still hot, the sensor is still open circuit, but once it cools off, the resistance comes back into spec, thus the car starts.

Parts

W220 uses magnetic impulse triggering sensor with two wires.

• OE part A0031532828 (~125EUR)
• Bosch part 0261210170 (~50EUR)

DIY Replacement

Torx screw in E8 torx female socket.

CPS location.

CPS electrical plug.

CPS attached to engine.

Removing screw using ratchet.

Tools needed:

• E8 torx 1/4 socket.
• Ratchet with 6-inch 1/4 extension.

Steps:

1. Remove engine cover.
2. Unplug the electrical connector from the CPS sensor.
3. Remove bolt using E8 torx socket.
4. Install in opposite order.

Note: If a heat shield is installed, there may be too small space for hand to fit. The way around it to not actually remove the connector, but just blindly remove the E8 torx bolt and use the connector and line to fish the CPS out.

Load video YouTube YouTube might collect personal data. Privacy Policy ContinueDismiss CPS replacement on pre-facelift.

Load video YouTube YouTube might collect personal data. Privacy Policy ContinueDismiss CPS replacement (including heat shield removal).

DIY Testing CPS

CPS can be tested by measuring its resistance and checking whether it generates voltage.

Load video YouTube YouTube might collect personal data. Privacy Policy ContinueDismiss Testing CPS resistance.

Load video YouTube YouTube might collect personal data. Privacy Policy ContinueDismiss Testing CPS voltage generation.

Resources

• http://www.mercedesmedic.com/crank-shaft-position-sensor/
• http://www.benzworld.org/forums/w220-s-class/1307031-2000-s500-problem-please-help.html
• http://www.benzworld.org/forums/w220-s-class/1496096-diy-cps-write-up.html
• http://www.benzworld.org/forums/w220-s-class/1635675-how-replace-cps-crankshaft-position-sensor.html
• http://mbworld.org/forums/s-class-w220/326637-how-replace-crank-position-sensor-cps-s500.html