Arthur Daltons' explanation is right on the money. In regard to how long it takes for the CE light to come back on, a few things must be considered. First, DM is looking for a certain RPM/vehicle speed to be reached. This is how it knows the upshift has actually been delayed. Next, the upshift delay isn't needed unless the engine is stone cold. If you were to start the car and let it warm up for a few minutes, DM wouldn't even run the test. Next, the engine load must be below approx. 50%. If you drive with a heavy foot immediately after start-up the test isn't run. Finally, the self-test must fail on two consecutive "trips" or "drive cycles". A code will be stored after the first failure but the CE light won't come on unless it fails twice in a row. I hope this helps.