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2018 Ford Escape 2.0 Ecotec. code P0171 and P0300. Long term fuel trim is flat lined at +29, Short term fuel is fluctuating from +1 to +5. Bank 1 sensor 1 O2 sensor is flat lined at 1.23 volts. Has had 02 replaced with no change. Smoke test system no vacuum leaks found. No other codes stored.
It is important to note the trim values across the operating range of the engine. Are these positive trims at idle only, under load?
Bank 1 sensor one is an AFR sensor, not a traditional 02, so don't count on seeing much in the way of changing voltage. Are there any other codes or symptoms?
If it's lean under all conditions, I might suspect a MAF issue. You can give it a wide open throttle pull through the 1-2 shift and check that the load PID reaches near 100% and check to see if the b1s2 stays rich or lean during this pull.
If load is low (below 80%) you can try to clean the MAF and check for improvement
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