2003 jimmy

[1985kenworth]

Hello i have a 2003 jimmy sls model and i have spent 100's of dollars on this truck about the emmissions...last year i bought a new exhaust system from the manifold to the tailpipe as well as o2 sensors and it passed emissions but a month after the engine light came back on and has been on since.people have suggested i replace the gas cap.i did with a locking one and nothing changed