SL/R230: Crankshaft position sensor- CPS
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Joined: Apr 2017
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2001 SL 500, 2005 ML 500
Crankshaft position sensor- CPS
I have 88,000 miles on my 2001 SL 500. Six months ago I had starting problems after coming out of a store 15 minutes later and diagnosed it as a crankshaft position sensor. I replaced it and everything was great for the next four months when the day after having my emissions checked at a state inspection station I had the same issue. I replaced the CPS again under warranty and all was great until two months later I had the same issue again. I poured water in the area of the CPS, the car started up and I drove home. Now what do I do? I've replaced two CPSs in 6 months so I'm thinking something else is wrong. Engine temps are within the normal range of 80 to 90 Celsius but I haven't replaced my coolant in at least 3 years. Any ideas out there? Thanks!
MBworld Guru
Joined: Dec 2009
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NO LONGER ACTIVE
Where are you buying these CPSs? I'd get either genuine MBZ, or genuine Bosch. Do not buy from Amazon or eBay - they sell cheap Chinese crap even though it may be labelled as Bosch. The CPS is subjected to a lot of heat and vibration, which are the enemies of sensitive electronic circuitry, so you need quality in this part.
If you are using a quality CPS, there may be another issues, such as a wiring problem or even a warped bell housing or flywheel. As you already know from replacing it, the CPS sits in the bell housing. It's positioned just above the flywheel (a.k.a. flex plate). The outer rim of the flywheel has "shutters" that the CPS's magnetic field detects as pulses, plus one longer shutter to determine TDC. If the flywheel is bent, that can interfere with the CPS's detection. If the bell housing is warped so that the CPS moves away from the flywheel, it can fail to get a signal. Another thing that can happen is that the magnetic end of the CPS can collect metallic debris, dirt or oil that can interfere with its operation. Any of these things means you have a mechanical problem that needs attention.
One final possibility is that there is a problem with the CPS seating into the bell housing so hat it does not protrude deep enough to make a proper reading of the flywheel shutters. This could be caused by improper installation, a poor quality CPS housing, or a bell housing deformation.
If you are using a quality CPS, there may be another issues, such as a wiring problem or even a warped bell housing or flywheel. As you already know from replacing it, the CPS sits in the bell housing. It's positioned just above the flywheel (a.k.a. flex plate). The outer rim of the flywheel has "shutters" that the CPS's magnetic field detects as pulses, plus one longer shutter to determine TDC. If the flywheel is bent, that can interfere with the CPS's detection. If the bell housing is warped so that the CPS moves away from the flywheel, it can fail to get a signal. Another thing that can happen is that the magnetic end of the CPS can collect metallic debris, dirt or oil that can interfere with its operation. Any of these things means you have a mechanical problem that needs attention.
One final possibility is that there is a problem with the CPS seating into the bell housing so hat it does not protrude deep enough to make a proper reading of the flywheel shutters. This could be caused by improper installation, a poor quality CPS housing, or a bell housing deformation.
