Hiccup when shifting

Hello, I have a 2005 vibe, automatic. Last week, my check engine light came on (has done this in the past with nothing identified as being wrong.) Took it in for an oil change as I noticed I was over due. The light turned off. Next evening, it was on again and there was a small hiccup when accelerating and shifting gears. Consistantly around 2000 rpms. My husband added an additive to gas last night. This morning, on my commute, it started fine but midway (about 20 minutes into 50 minute drive), the hiccup returned a little worse than before. Any suggestions?

Is this vehicle up to date with all of the maintenance recommended in the Owner’s Manual? Bringing a car up to date with maintenance will usually resolve driveability problems and random CELs.