Hi, I have a 2003 W210 Wagon which is behaving oddly. It doesn't respond to inputs at the gas pedal like it should. It has a VERY slow response, making the car extremely sluggish and dangerous to drive. It is intermittent, so I know it is a sensor or electronics. Not plugged cats or something like that. It happens when the car is cold and warm (but if I had to guess, I would say it is worse when warm). Before doing any code reading, I was guessing it would be a MAF sensor issue or a fuel pump/filter issue, but I guess I am wrong.

I just bought a Foxwell scanner with the 38 pin connector, and it tells me I have the following error:

B37 Accelerator Pedal Position Sensor (APPS) Signal 1/Short circuit to battery/potentiometer above maximum value/P0123.

I looked up P0123 and a Mercedes Fault Code pdf that I found says P0123 corresponds to: Throttle/Pedal Position Sensor/Switch A Circuit High Input

That is my only error so I assume that is the issue, but I cannot figure out for sure where this sensor is located. I think it is this item, but before I drop hundreds of $, I thought I should get your advice:
https://www.pelicanparts.com/More_Info/0125423317M375.htm?pn=012-542-33-17-M375&bt=Y&fs=0&SVSVSI=3817

Some bbs threads I have found on p0123 talk about changing out a sensor at the actual throttle pedal, but I cannot even find that in any of the parts catalogs.

Some online vids talk about p0123 referring to the throttle body on the engine, as opposed to the gas pedal.

Any thoughts? If it is that part which I linked to, is there any cleaning or maintenance I can do on the part? $200 for a no-name brand is a bit worrisome.

Thanks for your time.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).