not sure if its the o2 sensor and if it is where is it located on my truck which is a 96 Ranger 4.0 2wd

 

book says, lack of upstream heated 02 sensor switch sensor indicates lean (bank #2)

 

On the 4.0L of your vintage, seeing as how this is a lean code only for bank-2, (drivers side), maybe suspect a lower intake manafold gasket vacuum leak.

There were problems with the lower intake manafold fastners loosening up & the gasket being sucked in & causing a vacuum leak, assiocated with a partcular cyl bank.

Maybe rig a stethoscope with a length of tubing, or hose & have a listen in that area & see if you can locate a vacuum leak hiss.

If so & if the gasket hasn't been sucked in yet, maybe try re-torquing the lower intake manafold fastenes to spec & see if that helps.

OR, maybe you have a clogged, or operational fuel injector/s problem with that cyl bank, that the computer can no longer compensate for.

Anyway, something is amiss with cyl bank-2 fuel trim, such that the O2 sensor is saying the air/fuel mixture is lean & the computer can no longer properly control fuel trim for that cyl bank & the mixture is so lean the O2 sensor is no longer switching & it's signal is stuck at max lean.

Edit: If you have, or can come by a scantool that'll read PID's, maybe have a look at bank-2 long & short trrm fuel trim & post what you find.
Also have a listen to the bank-2 injectors with the stethscope to determine if you can hear one not clicking, erratic, or not sounding like the bank-1 injectors.

Let us know what you find.

 

I do have a scanner That has a freeze frame and it shows the following info for my truck's code

Trob code P1151
Engine (RPM) 1772
CALC LOAD (%) 50.6
COOLANT (Degrees in F) 181
LT FIRM1 (%) 2.3
ST FIRM1 (%) 0.0
LT FIRM 2 (%) 2.3
ST FIRM2 (%) 0.0
VEC SPEED (MPH) 43
FUEL SYS1 CLOSED
FUEL SYS2 N/A

 

OK, good, now do you have both bank 1 & 2 O2 sensor readings???

 

not sure what to look at on the code reader. I've posted all the info thats on my code reader. I just bought a fuel pressure gauge and just checked my fuel pressure with engine off key on and have 22 PSI and with Engine running only have 28 PSI. I also just bought a new fuel filter but haven't had a chance to change it yet. After i change it i will take new fuel pressure reading and post. Also bought some Mass air flow sensor cleaner and again have not clean anything yet but hope to do it this weekend.

 

Yup the fuel pressure is low as it should read 35-45 at KOEO.

At idle with the fuel pressure regulator vacuum hose attached, it should be 25-35 psi.
At idle with the vacuum hose disconnected 35-45 psi.

So be sure to pull the fuel pressure regulators vacuum line to see if it's wet inside with fuel & if so, replace the FP regulator.

Keep us posted on your trouble shoot.

 

OK, I've checked the FPR for gas in the vacuum line and its dry. Also checked the fuel ejectors with my stethoscope and everything sound OK but the front passenger side is a little weak but is ticking

 

Make sure the battery & alternator outputs are up to snuff & full B+ it's getting all the way to the to the fuel pump, so it'll have the designed for voltage to do it's thing.

Make sure the fuel filter isn't clogged & no crimps or kinks in the fuel line.

If all thats ok, & the FPR's vacuum line is in good shape, fits tight on both ends, then maybe suspect the fuel pressure regulator, or a weak fuel pump, or clogged up fuel pump pick up sock/pre filter.

 

Last night i cleaned the MAF sensor and another sensor just in front of the MAF Sensor and took for test drive after i cleared the code with my code reader. The code never came back on. So this morning i just changed the fuel filter and checked pressure readings and came up with still 28-29 psi at idle and 32 psi engine off key on. Also sprayed carb cleaner around intake and idle never changed. Does the FPR regulate fuel pressure before the test port or after? It my well be the FPR. Thoughts?

 

After installing the new fuel filter, what did the fuel pressure read, at idle, with the fuel pressure regulators vacuum hose Disconnected????

 

38 psi at idle with FPR vacuum hose disconnected and 28 psi connected

 

OK, good feedback, so after replacing the fuel filter the fuel pressure came up & from the numbers I posted above, it looks like the fuel pressure is ok & the fuel pressure regulator is doing it's thing, so it's likey ok, as you didn't find any fuel in it's vacuum hose.

I suppose the low fuel pressure could have caused the P1151 code, but it's strange that it would only affect bank-2 & thats why I was wondering what the O2 sensors output switching looked like, as the fuel trim numbers you posted didn't show a differnce in fuel trim for bank-1 & 2.

So maybe the new fuel filter getting fuel pressure back in spec, along with the EVR getting the EGR feedback right, along with your cleaning the MAF sensor, has gotten things back in trim, such that the computer is feeling better & is happy again!!!! lol

 

The fuel pressure regulator adjusts fuel pressure before the test port, or another way to think about it is, that the fuel rail test port is down stream from the regulator, or on it's output side, so the pressure number we read at the fuel rail test port, is the fuel pressure values the fuel injectors have to work with.

 

Ok just drove about 20 miles and the CE light came back on. Yep you guessed it its the P1151 again. here is the data from freeze frame again

Trob code P1151
Engine (RPM) 1452
CALC LOAD (%) 42.0
COOLANT (Degrees in F) 192
LT FIRM1 (%) 2.3
ST FIRM1 (%) (-2.3)
LT FIRM 2 (%) 2.3
ST FIRM2 (%) (-2.3)
VEC SPEED (MPH) 45
FUEL SYS1 CLOSED
FUEL SYS2 N/A