I've got a 97 Lumina that just popped out a SEL with several codes. One was a P0122 along with an EGR code and a Catalytic converter code. I replaced the TPS and waited for the light to clear which it didn't. Had it rescanned and came up with the P0122 code, P0140 and a catalytic converter code. Strange thing is that the EGR ,cat, and TPS have all been replaced within the past 2 years. Should I be looking at the downstream O2 sensor?