help w p0171 code

[surfranger]

hey all. new to this site and looking for some help.
I bought a 2003 2.3l ranger w 116k on it a few months ago.

when I purchased it it had the CEL light on, when I scanned it the P0420 code came up. A mechanic told me to replace the rear O2 sensor. I bought a new bosch downstream sensor, cleaned the MAF sensor, put in a new fuel filter, changed the plugs and wires, new air filter, and changed the oil/filter. I did this all in one day and just now realize I probably should have done them one at a time to see what fixed my problem. I disconnected the battery to reset the computer and yesterday the CEL light came back on w this PO171 code. any suggestions? thanks for the help

 

[modelageek]

hey all. new to this site and looking for some help.
I bought a 2003 2.3l ranger w 116k on it a few months ago.

when I purchased it it had the CEL light on, when I scanned it the P0420 code came up. A mechanic told me to replace the rear O2 sensor. I bought a new bosch downstream sensor, cleaned the MAF sensor, put in a new fuel filter, changed the plugs and wires, new air filter, and changed the oil/filter. I did this all in one day and just now realize I probably should have done them one at a time to see what fixed my problem. I disconnected the battery to reset the computer and yesterday the CEL light came back on w this PO171 code. any suggestions? thanks for the help

vacuum leak, fuel pressure...........I think your truck has some vacuum or pcv piece that rots out ....do a search

 

[surfranger]

Thanks for the reply. Can you be any more specific a bout what or where that vacuum leak might be and how to check it?