P0171 Buick -

Question

new pcv valve new front o2 sensor new air filter new oil and filter new map sensor clean maf and the service light still comes on. have no air leaks. what else could it be for the service light to remain off.

Answer 1

P0171 Fuel trim system lean Bank 1

Vacuum leak are the number 1 cause for system lean, leaks at the intake manifold is another possible area,  A degraded 02 sensor that becomes bias can set this code, Sparkplug codnition can also set a lean code condition.