Hello, ever since I bought the truck the ses light will come on once the engine is up to temp. I checked for codes and all I got was 12 and 13. I know 12 is supposed to show up. Code 13: Left bank O2 sensor circuit open or no activity. I replaced the stock o2 with a 3 wire heated o2. Wired to a a relay to turn on with the key. Drove it around the next few days and I'm still getting the code 13. What should I check next? I have verified that the heater works but turning the key on for about 5 min. It was pretty warm.