Go to the EC section, then "Diagnostic Procedure for DTC P0171." It will first check the MAF sensor (ground wire continuity), then the fuel trims, then the high-pressure fuel pump delivery volume. Do not change the O2 sensor first.
Want a printable checklist of torque specs for the E13? Download our companion guide: "E13 Engine Critical Torques & Fluids" (link). nissan e13 engine service manual