P0340 received this code after correcting code P0171

Question

P0171 (oxygen sensor - Bank 1. This code returned after replacing the sensor along with P0340 code.

Answer 1

P0340 Camshaft position "A" circuit

P0171 System too lean

If you get a faulty cam sensor the engine idles rough and lacks power ,and it will code P0171,(due to the rough idle).make sure the cam sensor connection male to female are proper,The CMP that is failing will cause P0171, Now in reverse a lean condition that that cause a engine hard to start will cause P0340, And this is where you need to check the fuel pressure, At idle the fuel pressure should be at 35 psi.