2.3L ('02-'11) TPS issues looking for guidance

[hannah2001]

I have a 2002 ford ranger with the 2.3. ever since i bought the truck (6 months ago) its been throwing codes P1120 and P1125. I just assumed it was a bad TPS (bad, i know) threw a new sensor on it but the code kept coming back. it has always had idling problems but was not giving me any drivability issues so I just decided to ignore it cause I don't have much time to diagnose nor the money to pay a mechanic to fix it. Well as of last week the truck has started bucking, jerking, shifting erratically, at one point i lost all throttle response going down the highway and i hit the pedal hard with my foot and its like it snapped back into it and started responding again. so now I feel like I have to actually try and pinpoint the issue since its giving me major problems, but I cant find much online as far as an actual diagnostic process for this specific engine and truck. People have talked about it could possibly be a failing PCM, wiring problems, could somehow be linked to the IACV or MAF, but no explanation as to how I can actually diagnose and I don't have the money to just throw parts at it.

what i've done:
- new TPS; unfortunately not motorcraft because I cannot find an OEM motorcraft sensor for this truck, i believe its been discontinued. I did get the most reputable brand I could find. I did attempt to calibrate it from what I could find online about holding the pedal down 3 times, i've also unhooked the battery and left it disconnected for 20+ minutes to do a full reset
- cleaned throttle body
- unplugged IACV while truck is running and warmed up, it idles terribly rough and at like 200 rpm so I believe the IAC is in working condition
- the previous owners tampered with the idle adjustment screw and had it backed all the way out. I dialed it back in the best I could and assuming by my sensor readings it seems to be set correctly.
- took TPS readings with forscan and I have attached a video of my results at the bottom of this post. the sweep seems to be stable and not jumping erratically

Basically what I'm asking for is guidance to how I can figure out whats causing my problem. I like to think i'm pretty mechanically inclined from not having the money to pay mechanics to work on anything I own (lol) so if someone could maybe write out all possible causes and step by step procedures on how to test all related components I would greatly appreciate it. I will answer any questions

https://youtube.com/shorts/cPuYwTjNZfU?feature=share

 

[franklin2]

I did a search on the first code and it came up with this


The diagnostic trouble code (DTC) P1120 in a Ford vehicle generally indicates a problem with the
Throttle Position (TP) sensor being "out of range". This means the Powertrain Control Module (PCM) or engine computer, has detected that the actual position of the throttle plate doesn't align with the desired position it's expecting.

Am I reading more into the above statement than I should? Reading between the lines, if the computer see's the TPS at a certain value, but there is more air going into the engine than the TPS position would allow, would that throw a code? Like having a large vacuum leak?

 

[hannah2001]

I did a search on the first code and it came up with this


The diagnostic trouble code (DTC) P1120 in a Ford vehicle generally indicates a problem with the
Throttle Position (TP) sensor being "out of range". This means the Powertrain Control Module (PCM) or engine computer, has detected that the actual position of the throttle plate doesn't align with the desired position it's expecting.

Am I reading more into the above statement than I should? Reading between the lines, if the computer see's the TPS at a certain value, but there is more air going into the engine than the TPS position would allow, would that throw a code? Like having a large vacuum leak?

i guess that could be possible. i'm not a mechanical guru by any means so whatever advice I get here I will try my best to follow. I've never had to find a vacuum leak on anything before and dont know how, i will read on it some tonight and hopefully within the next day or so try to find any on my truck

 

[hannah2001]

Everyone, i am so sorry to revive such a dead thread but over a year later and the problem is back. It never really "went away" but its been off and on, i've been able to clear the code and it would stay away for a few months and come back. Now it comes back within a day and it's getting worse. I believe it's making my transmission shift like garbage unless it's just my transmission going out (hopefully not). Transmission shifts hard, shifts erratically, doesn't want to downshift when passing, truck idles erratically, truck wants to surge going down the road. All possibly points to the computer not knowing where the throttle position is. This is still the only code I have.

On top of everything i've done in the original post above, I smoke tested through the brake booster hose at the intake manifold and found a vacuum leak at the back of the manifold. Fixed that. Still does it. I cleaned the MAF sensor. No help. New throttle body gasket. Nope

I dont know what else to do i'm at a loss. Someone said I could try replacing the throttle body but they're discontinued everywhere.

Is there some kind of specific way I have to install the TPS onto the blade for it to read right? Would it have something to do with the idle screw not set right?

at this point I'm wondering if it's a bad PCM. I have no idea how to diagnose that and I cant afford to just throw parts at it.

I attached photo of forscan with my voltage readings and showing the clean sweep again no spikes.

Does anyone have ANY advice? I will take anything at this point. Thank you

 

[alwaysFlOoReD]

What I'm telling you is just from what I have read...
That idle screw isn't. There is a procedure for setting up the TPS and "idle" screw, but I don't know it off hand. If you adjusted that idle screw it needs to be properly set again. Sorry I can't be more help.

 

[RobWigglezz]

Wiggle the tps connector while you sweep the throttle with forscan hooked up again. You should see if there's a bad connection. Also make sure the throttle shaft isn't over rotating the sensor. Unbolt the tps and hold the throttle wide open. Slip the sensor over the shaft and rotate it by hand to see if the bolt holes line back up.

 

[pjtoledo]

the TPS sensor is supplied 5 volt power ( VREF ) that also powers a couple other sensors or devices.
if one of those sensors or the wiring drags that 5v down the TPS output will follow it.
MAP, manifold absolute sensor & fuel tank pressure transducer are the other 2 devices.
MAP is in the valve cover at the rear. tank pressure transducer is in the fuel line under the bed.
you need to verify that 5v is stable. and the return to ground.

cylinder head temp sensor and power steering pressure switch also use a VREF, but they both come out
different pins from the PCM so I'm not sure they can affect the TPS VREF power. just something to be aware of.

 

[pjtoledo]

I have adjusted the idle screw at various times. if it's all the way out the throttle plate can stick shut.
adjustment for me was to set it to where the engine barely ran with the IAC unplugged.

 

[hannah2001]

Good information pj I didn't know that, will give me somewhere to start looking. And Rob I will do that when I get home from work. However let me get yalls opinion on this

Not sure how I missed this the first time but the voltage on the TPS should be ~.98 closed and 4.5 - 5v at WOT. I'm looking at my voltage numbers in the graph I posted and at closed it reads .63 and at WOT its only at 3.83. The code says "out of range" with these numbers it would be considered out of range. Could this be the entire problem? I need to adjust that stop screw until it reads .98v closed and 4.5v WOT?

 

[SenorNoob]

The only way to make that much adjustment is if the TPS screw holes are slotted...

Can you check your 5v line from the PCM? (or does that come from the GEM by then?)

 

[pjtoledo]

a bit more on the TPS:
it looks for a change in throttle input and the output level.
the TPS output is instantaneous and gives the PCM advance notice before the oxygen sensors can read
what actually came thru the engine and respond. the PCM adjusts fuel faster that way.

 

[pjtoledo]

The only way to make that much adjustment is if the TPS screw holes are slotted...

Can you check your 5v line from the PCM? (or does that come from the GEM by then?)

no GEM, comes from pin 90 PCM.

 

[pjtoledo]

Good information pj I didn't know that, will give me somewhere to start looking. And Rob I will do that when I get home from work. However let me get yalls opinion on this

Not sure how I missed this the first time but the voltage on the TPS should be ~.98 closed and 4.5 - 5v at WOT. I'm looking at my voltage numbers in the graph I posted and at closed it reads .63 and at WOT its only at 3.83. The code says "out of range" with these numbers it would be considered out of range. Could this be the entire problem? I need to adjust that stop screw until it reads .98v closed and 4.5v WOT?

detach the TPS from the throttle body. turn the inside full sweep. what readings do you get ?
the stop screw will not affect WOT

 

[hannah2001]

detach the TPS from the throttle body. turn the inside full sweep. what readings do you get ?
the stop screw will not affect WOT

With the tps detached from the throttle body and me turning it with my hand, lowest voltage is .72 and highest is 4.68

 

[SenorNoob]

That sounds right...

So why doesn't it reach WOT when it's bolted on? Were you moving it by hand at the throttle body or pushing the pedal in the truck? Maybe you've got the classic cable stretch?