Bought the car from a Ford dealership just three weeks ago. By all appearances, the car has been well maintained. While idling at a McDonalds after a brief interstate drive the other night, the Check Engine light came on. Gas cap is properly secured. Went to Advance Sunday morning and their reader gave the P0420. Their first suggestion was a cleaning additive for about $25. Paycheck hasn't cleared, so I didn't do that yet.

Car is definitely not lacking in power. A trip down US 119 and 50/250 Saturday showed that quite nicely. No odd sights, sounds, or smells.

Is this too soon for a catalytic converter to crap out? Is it more likely a sensor needing checked/replaced? Can I get away with just the cleaner?