I have a 2004 Cadillac CTS V6 In the last month when at a stop while the car is running fine we go to take off and the car does not want to go any faster then 40 mph. If you push on the gas the RPM's go up but the car does not go any faster. The last time it happened I had a buddy put his code reader on it and it came up with po 221 code and the check engine light came on. I shut off the car waited 10 sec started it back up and it ran fine. The check engine light stayed on for a day or so then went off on it's own. The car has not done it in a couple of days now but I'm worried that it will come back since it has done it about 6 times in the last month.