My dad said the Check Engine light was on in his car so I hooked up my Ultragauge and got 2 codes, P0171 and P0174. I cleared those codes then set the Ultragauge to monitor short term and long term fuel trim and drove the car around for about an hour. I assume that on a well running engine, the short term and long term fuel trim numbers should be pretty close for both engine banks, but on my dad's car it looks like the short term and long term fuel trim for bank 2 is a bit higher than bank 1. I also noticed that under moderate to hard throttle, short term and long term fuel trim for engine bank 1 will go to 0, short term trim for bank 2, sensor 1 usually stays at about 2.3-2.6, and the long term for bank 2 goes to 0. I'm not sure what to make of that information. Maybe a failing primary oxygen sensor for bank 2 of the engine?
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