won't shift into rev and park with pedal depressed




While early W209 CLK models also used a brake light switch however, on your 2006 CLK350 post facelift model, the brake pedal switch was eliminated and the BAS system is used to determine brake pedal application.




On your W209, the signal from the brake light system that releases the interlock comes from the brake system hydraulics.
I'm not privy to the specific details of the W209, but because you mentioned that the malfunction only occurs when parking on an incline, have you checked the fluid level in the brake reservoir? Also, I believe that the source of the signal is the brake hydraulic pressure switch located under the brake fluid reservoir.
My suggestion would be to search the W209 forum for further assistance.
Lastly, if needed, MB has provided a shift lock override capability, for which I've included the details, in an attachment below.




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