Dumb question, but are all your fuses good? Mercedes likes to tie strange systems on one bus.

The very first thing I would do is pul all the fuses and give them a good cleaning with either fine sandpaper, a fine wire brush, etc and reinstall them to be sure that they are all good and making proper contact. Often a MB fuse will look good but not be making actual contact from corrosion etc. Do it to make sure. Then go from there. many people have chased gremlins only to find a fuse was the issue. Check them all with a meter before reinstalling them to make sure they are good also. Good luck

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red

Fuses all look good. I went thru and gave them all a little wiggle, as I used to have to do with my old BMW E28 535is, just to be sure, but no change. No corrosion is evident, but I will go thru and clean contact points just in case.

My current theory is possibly a bad crankshaft position sensor. I will be looking into it as soon as I can get back to the shop; unfortunately, my Mother had a bad fall and I have been busy taking care of her, so may be tomorrow or the next day before I can test the theory.

Anyone know what a new CPS costs, by the way???

Thanks!
Brian

OK, CPS wasn't it... My friend who is helping me (BMW Certified tech, but pretty intuitive with most cars) has studied the wiring diagrams on Alldata and been over everything he can think of and believes it may be a failure of the DME/computer. Anyone have any problems with theirs? Is this typical? And lastly, soed anyone know for certain if the 500SL unit is the same?

Thanks,
Brian