2002 SLK32 w/67k mi.
Starts right up and runs well when cold but will just crank away when it's hot outside and/or after a good long run on hot days. Stopped dead at idle on a hot day once, as if suddenly switched off.

Error code gizmos not required in this situation

DIAGNOSIS: CRANKSHAFT POSITION SENSOR FAULTY

This is the third one that I have replaced in as many vehicles: 99 ML320, 04 ML350, now the SLK. the symptoms are always the same. Sharing my experience on this DIY adventure, with a shout out to lucky individuals with very small hands. The repair manuals call for removal of the air cleaner and all the hoses but this only gives you guys with big mitts a little extra room down there in the pit of despair.

Burn hazard: job must be done with engine cold.


CPS location is barely visible on the bellhousing flange, engine bay rear, driver's side roughly 10:00 if you were looking from the back of the car (photos). Identify the flex hose that the CPS wiring travels through and the heat protective cloth at the connector end of it that hides the CPS connector. You may need to cut off the zip tie that fastens the heat cloth to the flex tubing in order to slide it up and reveal the connector.





Notice that the connector seems sunk down deep in a well created by a black metal heat shield to the right of it, bolted to the bell housiing; this piece of steel must be moved aside in order to access the bolt below the CPS connector that holds it (unless you or your assistant have hands the size of a 2year old; either way, you still won't be able to get a socket in there to the bolt holding the CPS).

Loosen but DO NOT REMOVE the bolts holding the heat shield (E-Torx #14). If you remove the bolts and/or shield it will only increase your time and effort to re-assemble things down in that itty bitty tiny hand-chewing MF'ing space. You can see the lower grey bolt head in the center of the photo, between the blurry hose in the foreground and the black metal shield.



Back the bolts out with fingers on socket and short extension or adapter just far enough out WITHOUT REMOVING BOLTS COMPLETELY so you can slide the shield along the bolts to the right about 2"; the bolts are ~2.5" long. Unclamp the connector; the connector has a hinged clip on the top (squeeze down on the tab in the center of the connector toward the rear edge, then pull connector off (photo).



Loosen small bolt underneath connector soeket that holds CPS (E-Torx #8). You won't be able to see it so this is a job done by feel I used a 1/4" drive ratchet on a 4" extension down in there.
Remove and replace CPS and bolt. Do not overtighten; just snug.
Replace connector.
Tighten heat shield bolts. Do not overtighten; just snug.

Start car, take for a drive.
Repair manual calls for Star Diagnosis reset; I have not yet seen the need.
Check Engine Light will extinguish after 3 start-ups.

Hope this is helpful to someone.

 

Great post! I was guessing the ignition module

 

Hi,

I just wanted to thank you for this post, it helped out a lot. It wasn't quite a breeze. I had a lot of trouble getting under the sensor to get a good grip on the bolt. Had to remove the shield completely, and you were right about the ratchet, you absolutely NEED to use this.

Also. Destroyed my left hand. Mechanic's gloves would have been a plus. Still. Saved several hundred bucks because of this post. Hats off.