Rep Power: 0

I did a custom exaust from front to back a little while ago. Ever since I've had the check engine light on... when it came on right away, i took it back to the shop and they replace the o2 sensor; it stayed off for a bit, then came back on permenantly.... its been on ever since.. i just figured my car didn't know what to do with the new setup (i have an 1.7 el), has anyone else had this problem? and if so, how'd you fix it?
thanks all

 
Rep Power: 454

well first off do you still have the original cat converter on there? If you removed it and installed striaght piping, then the check engine light will come on cause you have no cataylst.

 
Rep Power: 0

jus reset it. i think you have to hold the pin in the culster while yuor starting on the car