• 1999 sierra fault code p0171 and p0174 Engine
• 1999 sierra fault code p0171 and p0174 Engine >> Chevy silverado codes p0174 code chevy truck. A p0174 is a code that says it all. • 1999 sierra fault code p0171 and p0174 Engine silveradosierra.com Chevy silverado codes p0174 code chevy truck. | p0174 2015 chevrolet silverado code tech notes the p0174 code means that more air than gasoline is detected in the exhaust gases exiting the combustion chamber. The lean condition can be caused by a vacuum.