What kind of minivan is it? Some, like the Honda Odyssey, have a feature that allows you to press in the trip odometer reset and hold it while inserting the key to "on" and letting the computer cycle through the codes. If the code is real, the light will come back on the next time whatever tripped the code before trips it again. If the code is a phantom code (or fixed), then the light blinks like it is supposed to, then turns off. Worth a shot.
A few VWs have a feature of unplugging a specific fuse while the engine is running, then restarting the engine after plugging it back in to reset the CIL. May want to google for more info on whatever your make is.
Currently enjoying my grandfather-in-law's 1966 A-code coupe. I am the second owner. Ü