My advice is related to the C36 M104 Engine in the W202 and will not be directly applicable to your car. However all Mercs were designed by Merc and carry the family genes!

You could try change the CPS Sensor with a known good one.

The next thing I would try is to change the coil with a known good one. (I have three coils in my engine and had to change one at a time).

Multimeter circuit testing the wiring from the controller computer to the CPS did not indicate any anomalies. This testing certainly didn't indicate the major breakdown of the insulation in the wiring to the CPS connector. But I do know that if I gently and cyclically tugged on the CPS wire that the engine would quit. The only other way I know to check the insulation is to cut open the coaxial wiring and thereby potentially destroying it. I am not sure if your car preceded the years involved with the Merc wiring debacle.

The Mercedes wiring repair solution for my W202 is actually called a Camshaft Connector in the EPS (both the camshaft and crankshaft use the same part number). The part number is A129 540 22 81 (the same as the number marked on the end of the connector body).

Testing the CPS wiring:


The embarrassment of Mercedes Green-friendly bio-degradable wiring (circa 1992-1996).
The green powder and silver flakes are the remnants of the internal coaxial wire insulation:


The Mercedes wiring repair solution for either the Camshaft or the Crankshaft Position Reference Sensor Connectors: