Thank you for pointing that out, there are two codes. First code is P138 which is "O2 sensor circuit high voltage". The second one is a little confusing. I triple checked it and it comes out as P1037. Unless I missed it, there is nothing like that listed in the manual. Drop the 1 and you have 037, "O2 sensor circuit heater 2 circuit low voltage". Does anyone have any ideas or thoughts?