I’ve had many problems with this truck, I replaced the DPFE, fuel filter, also cleaned the PCV valve. It originally had a p0401 code. I replaced the DPFE sensor and fuel pump is getting plenty of fuel to the rails. I deleted the old code and took it for a shakedown yesterday and all did good until the engine warmed up, then if started cutting out and I jumped on the interstate and all it would do was 50 and wouldn’t even allow 3/4 throttle before cutting out like choking the engine out. The only codes now they are left in it are the p1131 and p1151 codes. I checked for vacuum leaks, checked fuel pressure, and PCV valve, I did notice on the drivers side upstream o2 sensor that the outer sleeve protecting the wires is chafed and not sure if it’s just the outer sleeve or into the wires, but would it to run so bad that you couldn’t give more than half throttle and only pull a hill that’s 55 and only able to do it going 20 because of all the sputtering and trying to cut out. I did notice after I replaced the DPFE that the fuel pump, pressure, and idle are literally night and day difference. You can now turn it on with the first short crank, and idles like new. The p0401
code is gone and fixed the EGR issue, now I’m just left with bank 1 and 2 upstream issues. I’ve checked all that it could possibly be except actually unplugging wiring harness to the B1 sensor 1 o2 sensor to see if it rubbed into the wires. Thanks for the help everyone.

 

Welcome to the forum

P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
P1151 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2

Always good to post code numbers and definitions so we are on the same page

These are different than regular "lean codes"
"Lack of switching" is whats different
Regular lean code( P0171 System too Lean (Bank 1)) would mean O2 is working, changing voltage, but showing high oxygen that computer expected so its having to add more fuel than calculated

2000 Ranger fuel pressure should be 55 to 65psi, standard for 1998 to 2011 Rangers, 1997 and earlier was 35psi
So what is your fuel pressure engine running?

O2 sensors generate their own voltage
0.1v is high oxygen, or lean
0.9v is low oxygen or rich

0.0v would be lean and can be caused by broken wire or broken sensor
"Lack of switching" means voltage from O2 sensor is not changing even if computer adds more fuel

O2 sensors use a chemical reaction to detect oxygen in exhaust, and can't work until they are above 600degF
Which is why engine can run better cold until computer starts to use O2 sensor in its air/fuel calculations

O2 sensors are the ONLY sensors that wear out, they run out of the chemicals, 100k miles or 12 years which ever comes first is when they should be changed for new ones

You can get a Bluetooth OBD2 reader for $15 to see Live Data from each O2 sensor
Or if your current OBD2 reader has that function have a look at the voltage on each O2 sensor
If its stuck at 0.0v then its a wiring issue usually, but in any case get new O2 sensors if they are over 12 years old, they come with new wires attached

 

I had very low power and found a major exhaust leak as well as a misfire on one of my cylinders. Replaced o2's and now its like a brand new truck.