Check Light on and Cruise Control Light blinking

2007 Forester:  problem checked by mechanic and cleared several times, each time showing a different code.  Cleared recently but won't pass emissions because OBDII sections "not ready".  May need extension since renewal due soon.  Tomorrow will drive it following recommended drive cycle to reset all monitors, then have it retested.  Shop said could be expensive to find problem and there may not be one.  Car runs fine; has only 79,000 well-maintained miles.  Does this seem like right approach since I don't want to invest a large amount of money if the problem is only the computer but need to pass emissions by 12/31.