Two weeks ago I replaced the crankshaft sensor in my 2003 SLK 32 and I would like to share my experience. I hope it helps.
1. The problem:
Car wouldn´t start at first attempt. It started at second attempt.
Two weeks later after driving for about half an hour I stopped in a store for 5 minutes and then car wouldn´t start. All electrical accessories working including the starting motor. Wait for 10 minutes and car started. After 5 minutes engine cut off while driving. Again all electrical accessories working fine. I called road assistance and took the car home.
Next day I checked K40. It looked ok but I redo some of the famous soldering. Went for a ride and engine cut off while driving after 10 minutes.
This time check engine light was on. Connected the scanner and got the code (important: I had to turn on the engine for the scanner to get communication with the car. My Grand Cherokee only need to put the key in the on position without starting the engine).
Code P0335: Crankshaft Position Sensor A Circuit Malfunction.
3. The sensor:
Visited several auto parts stores and I only found an alternative sensor in stock. I purchased it in O´rielly for $56. Bosh sensor was around $36 but was not available and I didn´t want to wait 10 days for it.
The location of the sensor is on the back of the engine on the driver´s side.
The sensor is hidden by the connector´s heat protection which has to be loosen by cutting the cable tie. Do not remove it. Just cut the cable tie that holds it in position and move it away of the connector.
Disconnect the cable to reach the sensor. The connector has a latch to secure it in place. Be careful not to break it.
Remove the sensor using the E-8 Torque wrench and a lot of patience. The bolt is right under the connector of the sensor itself and it´s very difficult to reach. I recommend to use gloves to protect your hands as the space is very limited. You may need an extension as well.
This how it looks without the sensor
Here is a side by side comparison between the removed sensor and the new one. I´m assuming the removed sensor is the original one but I´m not sure as I´m the third owner of the car. Both sensors are exactly same size and shape so the new one fitted without problem.
Install the new sensor. It is very tricky to reach with the bolt and the wrench down there. I used a piece of clear tape to prevent the bolt from falling from the wrench as it is impossible to reach there with two hands. Once the bolt was tighten I removed the tape. A magnetic wrench would do that job as well.
I finally connected the sensor and installed the heat protection again.
It is a fairly easy DIY project but requires some patience. It took me around an hour to do the job.
After the replacement I have been driving the car for two weeks every day without problems. The check engine light went off by itself.