what does codes p1405,po171 and po174 mean

P1405 DPFE Upstream Hose Off Or Plugged P0171 & p0174 are both engine lean codes (for both sides of the engine) The BDFE controls the EGR valve based on what it thinks the flow is. If that is wrong, performance suffers. I would recommend removing the DPFE Upstream Hose and inspecting for blockage. Chances are it is stopped up (which is what is also causing the lean codes).

All three of my explorers had the idiot light 171 and 174. After pulling my hair out the first the neightor who was a Ford mechanic told me to clean the intake and throttle body with cleaner. Also stated to clean the electrode on the MAF sensor with spray cleaner. Did so and the problem cleared up each time. Be careful, the small wire on the ensor is the width of a hair. If you break it another sensor is not cheap.