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Pelican Technical Article:

Camshaft Position Sensor Removal

Kerry Jonsson

Talent:

*

Tools:

5mm Allen head socket with ratchet. Pliers, pick

Applicable Models:

Mercedes-Benz R129 (1990-02)

Parts Required:

camshaft position sensor

Hot Tip:

Tap Allen head socket into fastener to help prevent stripping

Performance Gain:

repair check engine light, repair extended crank

Your camshaft position sensor does just that, it gives the position of the camshaft left side intake camshaft as it goes through its rotation. On the early models 1990-1993 (our car) there is only one camshaft position sensor on the left side head. In 1994-1998 Mercedes Benz used two cam sensors one on each cylinder head mounted in the same position.

The procedure to remove the camshaft position sensor on the right cylinder head is identical to the procedure to remove the camshaft position sensor on the left side cylinder. Mercedes Benz uses a pulse-generator style cam sensor. This means it has a magnetic winding in it and it generates an AC pulse as a toothed wheel passes by. This engine has variable valve timing on the intake cam. The control unit looks at the position of the camshaft and compares it to the position of the crankshaft. When the variable valve timing is de-energized the cam shaft position sensor and crankshaft position sensor have a certain relationship. When the variable valve timing solenoid is energized the relationship between the camshaft position sensor and the crankshaft position sensor changes. The control unit can compare the cam/crank relationship with the variable valve timing solenoid not energized and the variable valve timing solenoid energized. The engine control unit uses the cam sensor to see if the variable valve timing actuator is advancing the intake cam gear relative to the crankshaft.

In this tech article we will show you the steps to test and replace your cam sensor. 

Here we are at the front left cylinder head of the engine on the intake manifold side we see the camshaft position sensor (green arrow)
Figure 1

Here we are at the front left cylinder head of the engine on the intake manifold side we see the camshaft position sensor (green arrow)

There is a metal snap ring that holds the camshaft position sensor plug to the cam sensor.
Figure 2

There is a metal snap ring that holds the camshaft position sensor plug to the cam sensor. You may want to use a pick to remove the snap ring. This will make it easier for the connector to come off.

Squeeze the connector and pull it away from the sensor.
Figure 3

Squeeze the connector and pull it away from the sensor. The plastic on the sensor is brittle and it may crack. ThatÂÂÂÂ's why we recommend removing the snap ring first.

Use your 5mm Allen head socket or wrench to remove the two mounting fasteners (green arrows).
Figure 4

Use your 5mm Allen head socket or wrench to remove the two mounting fasteners (green arrows).

Rotate the sensor slightly and pull it out of the cylinder head.
Figure 5

Rotate the sensor slightly and pull it out of the cylinder head.

The sensor is wired like a coaxial cable so the middle terminal is the signal wire and the outer ring is the ground connection.
Figure 6

The sensor is wired like a coaxial cable so the middle terminal is the signal wire and the outer ring is the ground connection.

Measure resistance between these two points and you should read the following:
Figure 7

Measure resistance between these two points and you should read the following:


Camshaft Position Sensor (terminal 7 and 31d) 680-1200 ohms
Camshaft Position Sensor (terminal 7 and Ground) >19

Installation is the reverse of the removal steps. Fit the sensor in the cylinder head and tighten down the two mounting screws. Install the snap ring on the electrical connector and plug the connector to the cam sensor. Clear engine codes and see if any codes come back.

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Comments and Suggestions:
Jack Comments: I don't understand half this article. You discuss the Camshaft sensor, then the resistance levels in the last paragraph refer to the crankshaft sensor. Can you advise us what the resistance readings of a good camshaft sensor should be? thanks
June 29, 2016
  Followup from the Pelican Staff: That is a typo, thanks for catching it. I will have it updated. - Nick at Pelican Parts  
Greg Comments: I appreciate your technical articles on the SL500 1993. However, in the article to remove and test the Camshaft position sensor. In the last paragraph you have the resistance should read XX ohms. You need to insert a value.
Hoping you can help.
Greg
March 22, 2016
  Followup from the Pelican Staff: Thanks for catching that, I will have the article updated.


Crankshaft Position Sensor (terminal 7 and 31d) 680-1200 ohms
Crankshaft Position Sensor (terminal 7 and Ground) >199 ohms - Nick at Pelican Parts
 

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