having issue with fuel consumption--using a lot more fuel than normal on 2002 Pontiac Grand Am

any ideas where to check first? regular maintenance and changed the timing earlier this year just because the car was getting a lot of miles beginning noise
car seems to have been running fine but noticed the last week or so that it is drinking gas --any ideas?
parts need to be checked or changed? tune- up?

Asked by for the 2002 Pontiac Grand Am
scan for eng codes and ck fuel trim with scanner or get diag from your mech