Question

1999 Honda Accord V6 with engine code P0171, how to replace senor?

Answer 1

P0171 Fuel trim lean Bank 1

This is a condition of the engine, meaning there is more air than the fuel ratio, this mosty are caused by vacuum leaks, such as vacuum hoses that are not connected, to 02 sensor being biased, and in some condition the sparkplugs where its spark gap is out of it range.

Answer 2

P0171 Honda Code - Fuel Injection System Too Lean Bank 1
Read more: https://www.autocodes.com/p0171_honda.html

P0420 Honda Code - Catalyst System Efficiency Below Threshold
Read more: https://www.autocodes.com/p0420_honda.html