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Crankshaft Position Sensor Replacement
 
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Pelican Technical Article:

Crankshaft Position Sensor Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$130

Talent:

*****

Tools:

Set of sockets, E8, flathead screwdriver

Applicable Models:

Mercedes-Benz E320 (2003-05)

Parts Required:

Crankshaft position sensor

Hot Tip:

Work with a cool engine

Performance Gain:

Car will start and run well

Complementary Modification:

Replace air filter

A crankshaft position sensor is an electronic device used to monitor the position or rotational speed of the crankshaft. The crankshaft position sensor is used to synchronize engine timing for fuel and ignition control.

The crankshaft position sensor takes the place of distributors on earlier engines.

The crank sensor is used in conjunction with a camshaft position sensor to monitor the relationship between the pistons and valves in the engine. This method is also used to synchronize a four-stroke engine upon starting, allowing the management system to know when to inject the fuel and into which cylinder. It is also commonly used as the primary source for the measurement of engine speed in revolutions per minute (RPM).

It is located on the left rear of the engine, mounted in the transmission bell housing. The sensor reads a toothed reluctor wheel mounted to the end of the flex-plate or flywheel. It then sends a signal to the DME used to identify cylinder location. If this signal is missing, for example from a faulty crankshaft sensor, the engine will not start. You can consider the signal from the crankshaft sensor the RPM signal for the DME.

In this article, I'll go over the steps involved with replacing the crankshaft position sensor. You can access the sensor from above the vehicle, working on the left side. For information on testing the crankshaft position sensor, see our tech article called crankshaft position sensor testing.

Remember your car may have been serviced before and parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

The crankshaft position sensor is located on the left rear of the engine (red arrow), mounted in the transmission bell housing (inset).
Figure 1

The crankshaft position sensor is located on the left rear of the engine (red arrow), mounted in the transmission bell housing (inset). 

Working at the engine cover (red arrow), pull off the two front air duct hoses (green arrows).
Figure 2

Working at the engine cover (red arrow), pull off the two front air duct hoses (green arrows).

To detach the ducts, pull them straight off the engine cover / air filter housing.
Figure 3

To detach the ducts, pull them straight off the engine cover / air filter housing. Then pull the front of the duct out of the radiator support and remove it from the engine. Repeat this step for each duct.

Lift up and remove the front engine cover.
Figure 4

Lift up and remove the front engine cover.

Then, pull the engine cover / air filter housing straight up to remove it.
Figure 5

Then, pull the engine cover / air filter housing straight up to remove it. The cover is held on by four metal clips that grab onto rubber mounts, with the front two shown (red arrows). The rear of the cover has two as well. Once detached, remove the engine cover / air filter housing from the engine.

Working from above the left side of the engine, reach down behind the cylinder head.
Figure 6

Working from above the left side of the engine, reach down behind the cylinder head. Disconnect the crankshaft sensor electrical connector (red arrow) by pressing the plastic release tab and pulling it straight off.

Next remove the crankshaft sensor E8 mounting fastener (red arrow).
Figure 7

Next remove the crankshaft sensor E8 mounting fastener (red arrow). There is not a lot of room, so I use an extension with a swivel attached to the E8 socket on my 1/4-inch drive ratchet. Use a mirror before you remove the sensor. If you see debris like shown here (yellow arrows), use low-pressure air to blow it away from the sensor. You want to make sure that the area is clean before removing the sensor so nothing falls into the hole.

Once the fastener is removed, pull the crankshaft out of the engine block.
Figure 8

Once the fastener is removed, pull the crankshaft sensor out of the engine block. It will slide straight out (red arrow). I have not seen one stuck or frozen in the bell housing before. This can happen due to corrosion. If it does, spray the sensor with a penetrating oil and let it soak. Then try again. Rotate the sensor to break it free and then remove it.

This photo shows the sensor removed.
Figure 9

This photo shows the sensor removed. Install a new sensor and tighten the fastener. Reconnect the electrical connector and install the engine covers. Start the vehicle and allow it to idle for about 1 minute. If your check engine was ON, now is the time to clear any fault codes. You are now finished. Good job.



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Comments and Suggestions:
Designerlarsb Comments: Is this going to be the same on an E500 w211?
December 3, 2016
Bstrom Comments: Figure 8: Once the fastener is removed, pull the crankshaft out of the engine block.

This isn't correctly stated - you're pulling the CPS out of the bell housing, aren't you?
October 10, 2015
  Followup from the Pelican Staff: Yes, the word sensor is missing from the statement. I will have the article updated. - Nick at Pelican Parts  

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