BiFuel F150 Engine Codes P1131 & P1405

[farns]

Good afternoon!

I'm having some difficulty with my F-150, and not having a lot of luck searching up the engine codes here in the forum. Maybe I wasn't doing it right, but I search up both engine codes separately and got zero results. I hope I'm not the only one on the planet with this problem LOL

My truck is a 2000, bi-fuel (CNG - factory built, not a conversion). My CEL has been on for months, and now it's time to get my tags renewed, so I need to deal with this. The two codes I'm pulling are:

P1131 -- Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1

P1405 -- Differential Pressure Feedback Electronic Sensor circuit Upstream Hose

After disconnecting battery for 20 minutes, it only took about 20 miles for the CEL came back on. There was a 3rd code when I checked before I reset it, but it hasn't come back yet (180 miles after the reset) and I've lost the post it note I wrote it on.

I'm quite worried about the P1131 code, because the wording in the code sounds a lot like the infamous Windstar problem that I was able to solve a few years ago by reading this thread from the Windstar forum: http://leckemby.net/windstar/windstar01.html

I really hope it's not the same thing. I don't know that I have it in me to tear another engine apart. I'm the worst with car repairs, I only did that one because of the great walk through that pcitizen posted. Took me 3 solid days!

Does anybody have any thoughts on what these codes mean and where I need to start to address them? Thanks!

Farns