Po171 problem for 1999 Toyota prerunner

Question

Check engine  po171 detected

Answer 1

P0171 Fuel trim lean

Vacuum leaks are the common cause for a lean code condition, and with Toyota the sparkplug gaps should also be checked as well

​ The MAF airflow duct should be inspected , any tear here would allow false air to get pass the MAF sensor and set a lean code condition