2004 Nissan Altima 2.5L codes p0223 and p0123 put in used engine and have done relearn process many times. have 5v reference at the sensor and also the computer. grounds are good and need some advice to cure the problem
have you cleaned the throttle body? idle air relearn does not do anything if there is carbon buildup on the throttle plate which causes resistance and set the light on
if you have not clean it try that first. if the problem is still there, the throttle body might be bad (the carbon buildup will create resistance and damage the throttle position sensor.
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