California or Federal emissions?

Let engine warm up. Operate engine at 2500 rpm for 90 sec. With engine at 2500 and after 90s take both O2 sensor voltage readings between their high and low voltages. The range of voltage can help determine if the sensor is working OK.

 

California emission. What's interesting to note regarding this P0171 issue, is that after a few minutes of warming up while driving, the Bank #1 Long and Short-term fuel trim levels are not as high and seems to drop from 50% to 10%.

 

Do you have Bank 1, Sensor 1 voltage info?

Does the scanner read coolant temp? If so at when temp does the trim drop?