You'll attract more flies with honey than you will shit... if advice is not usefull, please try to keep it to yourself... otherwise no one will feel like helping you. I've already noticed this community seems to ignore threads w/o comments in reply to the OP... I'm pretty sure you don't want them to ignore posts created by your user name.
Having given my etiquette bit... I'd suggest getting your hands on an Ohm meter and ensuring you're getting the right input and receiving the right output values. Code 21 could be o2 sensor, o2 sensor heater, or your ECU... checking the rate of ohm's thru the parts might help determine where the problem is.. I hope it's not your ECU... that's a big fear of mine regarding my mk3, and I wouldn't wish that upon anyone... good luck, and update this thread based on your findings.. people can generally give better help/advice when there is more details that are included... also, the more specific the detail, the better...
