Hi guys I have a 99 slk and my check engine light came on on the way back from the Oregan Coast. I put my reader and got a P0170 error Fuel Trim Malfunction (bank 1)

does anyone know what this means?

 

O2 sensor may be bad. Did you happen to over fill the gas tank or switch to a different brand gas. Try clearing to cel and see if it comes back.

 

I did switch from Chevron to Shell on the way to the coast, but only because I was running low and didn't know when another Chevron would come up. I know toping up is really bad for the car so I wouldn't do that. I think it might be my MALF, I took it out and sprayed it and reset the computer car seem to run as before. hope problem doesn't come back