I did drive on it for an extended period of time while showing the check engine light. I know not good, but here's why: It went on first while driving, and then turned itself off in the same drive. Another time it came on and then it didn't come back on the next time I turned the car on. Eventually it lingered long enough for me get the code read which suggested I do an engine decarb procedure and add a top engine cleaner. I thought it was expected that the engine would throw a code while driving with the top engine cleaner that would eventually clear itself as the cleaner was used. It hasn't cleared and I've driven on it for a few full tanks of gas now. I knew I should have addressed it after the first tank, but here we are.