I have a ’97 Eldorado ETC that I picked up at an auction this week. It has current PCM Codes of: P0135, P0139, P0146 & P0155. I looked these codes up and if I’m not mistaken, they are all O2 sensor codes. Given that it is highly unlikely that all O2 sensors are failing, I wanted to reach out to the experts in this forum for some input. Thanks in advance for your help! cal