Hello MarekW, I am having the same problem as you. I have a 2001 Mercedes-Benz C320 Base sedan in the shop right now. This also has code P202e. Your throttle is in limp mode. The code P0120 is a generic code that covers about 6 different throttle codes. The P202e version specifically states, "CAN message from AAC [KLA] control unit/comfort automatic air conditioning (N22, N22/7), CAN signal discontinuity (-)." From what I understand, the engine control module isn't getting the communications it needs from the ACC control unit (for air conditioning). I believe it needs to know AC compressor torque, Refridgerent pressure, and something else that I can't remember at the moment. What I do know, is that the ECU communicates on CAN C(100hz), and the ACC communicates on CAN B(84hz). There are three modules that communicate between both CAN frequencies, the Instrument cluster module, the steering angle module, and the EIS (EZS) control unit; however, the EIS control unit is the only one that acts as a "gateway" for control modules on differing CAN frequencies. The EIS control unit is the one that the ignition key physically fits into. I hope this helps. The C320 I am currently working on did the exact same thing that your Mercedes is doing. Erasing the ECU codes didn't make a change, BUT, erasing the codes from the ACC (KLA) module let the car drive perfectly. I am still currently trying to find where the actual fault resides. I haven't finished testing yet, but I wanted to give you a heads up. I have tested my throttle actuator and accelerator pedal position sensors and they all test good.
-Aaron
ASE Master Certified
ASE L1 Advanced Engine Performance Certified