UKPassats

So had my throttle body replaced as per other post i had on here a while ago as thought it was EGR issue, wasnt turned out to be needing a new throttle body, replaced it emmisions light went out for a few weeks drove lovely, however on saturday went to take the car out stupid emmisions light back on, car instantly went into limp mode, so have left it over the weekend spoke to my mechanic he said bring it over on monday, so got in my car to come to work this am emmissions light on but when i drove off no more limp mode and car seems to drive fine, so gonna get it scanned later, what could the problem be this time, the throttle body clearly fixed it could it be a sensor or just thrown a wobbly and needs clearing!!!

im begginning to get a bit annoyed with vw in general now as my polo has light on it too!!!!!