caddypete Posted October 19, 2005 Report Share Posted October 19, 2005 My 2000 eldo gives me a SES light, when I get the codes it shows bank 1 fuel trim lean,and Heated Oxygen Sensor Insufficient Switching Bank 1 Sensor 1.I replaced the o2 sensor with a Bosch and it gave me other codes P0131 - Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 1 Sensor 1, I was told that caddys don't like the bosch sensors, so I replaced it with a AC delco.The bosch o2 sensor was black sooty which indicates that it is running rich to me.I still get the service engine soon light with the codes lean bank 1, and Heated Oxygen Sensor (HO2S) Insufficient Switching Bank 1 Sensor 1. Had a freind put a scan tool on it he read bank 1 was beng richened by +.20 by the computer and the o2 sensor on bank 1 was barely moving between .15-.19 while bank2 was constantly moving and at a much bigger swing like he said it should be. the cat 02 sensor was reading slightly rich. My question is if bank 2 is running correctly and bank 1 is reading lean and the cat 02 is slightly rich. How is it possible bank 1 is being detected lean by the computer?When I pull the o2 sensor out of bank 1 it is black sooty like a rich spark plug would look. Where do I start? what am I looking for?I have checked for a vaccum leak on that bank, found none. Am I correct in thinking bank 1 is the one closest to the firewall? Link to comment Share on other sites More sharing options...
Ranger Posted October 19, 2005 Report Share Posted October 19, 2005 About all I can tell you is that you are correct on the bank numbering. I never really did understand this fuel trim stuff and will be looking forward to the explanation. Link to comment Share on other sites More sharing options...
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