2005 Kia Optima LX with check engine light on

My timing belt broke and I had it replaced and then it wouldn’t crank so they replaced the crankshaft sensor. It cranks and runs find but the check engine light is still on. The mechanic said the light should go off soon. But I am not sure if I believe him. It is reading code P0338 when I took it to Precision Tune. Do you think my codes just need to be cleared? And if so, how do I clear them. I did the visual inspection with my oil change and every thing came up fine