I've started a thread on how to evaluate the CPS at Benzworld. Here's the link:
http://www.benzworld.org/forums/w163-m-class/1282808-cps-evaluation.html?highlight=cps+evaluation
Here part of the post:
The following is my opinion and I welcome any comments and suggestions. I'm posting this because I am getting the impression that many people point to the CPS as a problem when their vehicle doesn't start or stalls. Even though this area is a potentional cause for no starts or stalling one should not assume that it is the only reason and many replace a perfectly good sennsor for no other reason than to hope that it solves their problem. The CPS can fail for many reasons and they do fail. Heat can be an cause for CPS failiure (I've tested one on a bench with a torch applied to it and measure the effects of heat on it's resistance and there is a noticable change.) but it can also be flywheel damage, debris on sensor, installation, etc. The only definitive way to rule out the CPS is testing which is not difficult. Measuring the resistance is a poor test which is too general. The best way to test is to use a scope (oscilloscope) to observe the waveform and output. Please see the attached image from a W126 WIS. On this application, the output (Us) must be greater than 1 volt. If the computer does not see this minimum requirement then it won't know when to time the car! I do not have the W163 WIS so I cannot compare the differences but the concept should be the same.
Comments?
DL