need some advice about check engine light

My check engine was on and I i went to a mechanic and he said that it was the EGR Flow sensor(I think that is what he said). He said he reset the codes and drove it around the block and he said that the light didnt come back on so it should be fine. Well now the light is on. I really cant afford a 500 dollar job could anyone tell me how much the part should be and does it need to be fixed right away?

repull the cel to see if it is the egr again. the egr cel can be caused to plenty of things that need to be checked. but, to make ease of what people are looking at, year, make, and model would be nice assuming your car is stock.

1997 Civic (HX I know crap) Stock except some body work

clean the areas around the egr and inside of the egr valve with carberator cleaner, or you can just replace the valve. reset ecu and see if that solves the problem.

if that doesnt work, then, your going to have to check the vacuum lines to the egr valve, the egr solenoid, and the egr lift sensor. but, before coming here, you should do the above first.

also, your mechanic just pulled the code or he already actually checked the egr system?

check the o2 sensor too that will cause the egr to go bad