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2000 230 slk sudden engine shutdown problem

3K views 1 reply 2 participants last post by  Subby_ 
#1 ·
While driving this car the engine suddenly shuts down causing the car to quickly decelerate to a stop. Engine won't turn over, but car has normal power.

Trouble code readings show possible problem with the K40 relay, among other things. (possible PSE pneumatic control module problem)

The notorious K40 relay is a well-known cause of starting, idling, and engine stumbling problems.

I decided to start with it. It was easy to locate and very easy to remove. I did not disconnect the battery but you probably should. (This car has a history of blowing a particular circuit board when the battery gets charged/disconnected, so I took a chance in not disconnecting)

I used several screw drivers to hold back the plastic enough to open the box, and extracted the relay circuit board. Upon first look, the board looked pristine--No damage anywhere, clean as can be. I decided to use a magnifier to inspect the solder joints. Please see the attached images to see what I found.

There were three pairs of contacts on the left side of the circuit board that clearly had bad solder joints. They were "cold soldered", which means the pins sticking through the board did not get hot enough during manufacture for the solder to adhere properly. If this isn't the problem that is causing my engine to shut down, it is still a problem needing to be fixed.

This is easily a problem that a do-it-yourselfer can fix.

I suggest using at least a 700 degree Fahrenheit soldering iron (you need to get these pins hot), flux (buy some!) and a tiny bit of extra solder to re-solder your connections if they look like mine. If you look around on the internet you will find this is a common problem.

The attached photos should be helpful.

I'll post back if this resolves my engine fault issues.
 

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#2 ·
the K40 is the biggest problem with these cars... given there age now im pretty sure most forum members have repaired or replaced this module.

first place to check if things go wrong..
 
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