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Discussion Starter · #1 ·
Symptom: 98 C230 stalls after warming up and restarts after ~30 min cool down
Fix: Replaced crankshaft position sensor (CPS)

Attached pdf file: Replacing CPS on 98 C230 without removing starter motor and some notes on testing the CPS.

See attached pdf file, here is the text,
Bottom left pic is view looking in direction of yellow arrow above showing starter motor.
Lay under car, feet to front, pull cable shown down to make room, reach up above the starter with your left hand where the mirror is in the bottom right pic. Feel for the round connector on the CPS and pull it off, then feel for the 5mm allen screw. You can get a standard size, short 5mm Allen wrench on the screw with enough room to loosen it about ¼ turn, then unscrew it by hand. Then pull the CPS out. You can barely see the CPS in the mirror in the right pic below. You can’t see it but you can feel it well enough to remove and reinstall it without removing the starter motor.

Some notes on testing the CPS.
- Coil resistance is ~ 1.18K ohm, AC voltage when engine is cranking during starting is ~55mV.
- You can rig up an easy test lead using one of those long, thin, cheap, two-wire extension cords. Clip off the plug and strip the wire ends ½”. Slip one bare wire into a ½ inch long piece of ¼ inch id tubing, then slip that over the center connector on the CPS while holding the other stripped end between the tubing and the outer ground ring. The tubing acts as an insulator and holds the wires in place. Then insert the meter leads into the receptacle end.
I rigged up a test set with a drill to generate an AC output of ~100mV from the CPS and I could not get my bad CPS to fail when heated with a blow dryer, maybe not hot enough, but it was defective as the new part fixed the stalling problem.
I initially bought/installed a $26 generic CPS and the car would not start (coil =1.05K ohm, VAC out with engine cranking =33mVAC), figured it must be the lower AC output. I returned it for a $57 BOSCH part and that worked fine.

99 C280 Cranks but will not start - PeachParts Mercedes ShopForum (cps job * MANY MANY THANKS TO JRStew) (crankshaft sensor) (mass air flow sensor)

Hope this post helps someone. I still could not find the CPS on my 98 C230 after reading all other posts, so I posted this thread. Big thanks to all others who post symptoms and fixes, if you fix a problem please take the time to post the symptom and solution. Thanks, JC


2000 S430 (W220)
58 Posts
I want to start by thanking JC98C230 for writing excellent instruction for the DIY CPS replacement. Since most of the work is done by the left hand in replacing the CPS, I think southpaws may have an unfair advantage :)

In researching the warm start problem I would like to add that in my 1998 C230, I was not getting a CEL and so no codes that would lead to the malfunctioning CPS. The only clear cut symptom was that while running and once the engine temperature got around 85 degrees Fahrenheit, the car would simply stall out and would not crank until the engine cooled down. Any ways long story short I replaced the CPS and the problem seems to be gone. I followed the instructions in JC98C230's PDF to the T and was able to successfully swap the sensors.
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