I just finished removing 4.6l and installing 5.4l into my truck, so far I'm down to the nitty gritty stuff. I'm still using the 4.6l ecm.....the (PO122) code keeps coming on and I am lacking major power when heavily on the throttle, I can build torque upto 2000 rpm by pumping the throttle or backing off it once it starts to moreless choke out....almost like theres a choke open. Anyways I have tested and I'm getting 5volt ref, and on the other two ports are 11.5v and 10.5v....without any throttle load, I'm not getting any difference with load on the throttle also, I have replaced the TPS and theres no diff, whether its plugged in or not the truck still runs the same.

I'm curious if there's a way to reset the TPS or is it fully controled by the pcm? I'll be putting it on the dyno and reprograming it soon as I get all the bugs worked out of it.

2003 f150 4x4

99 5.4l converted engine (from a van)

thanks for help ahead of time

 

The hookup on both systems is the same.
You have a harness or connector issue.
The TPS is just a vairable resistor that could have been tested with an ohmmeter instead of buying a new one.
How it works and why the motor would have drivability issues without it working.
This device signals the PCM as an indicator of what 'you' are doing with the throttle and what the 'inferred' intent is to be.
Slow opening tells the PCM to add fuel.
Fast opeing tells the PCM to add a lot of fuel by the " rate of change" that takes place.
Position and length of time tells the PCM what to do with transmission shifting.
Position along with RPM tells the PCM what to do with transmission lock up and EGR functions.
Sudden return to an idle condition upon slow down tells the PCM to cut fuel and make sure the IAC stays open just far enough to keep the motor from stalling on slow down. These actions are assisted by the input of the speed sensor as well, to come to the logic decision for how to handle the slow down.
So you now see how important this simple device is to the total operation of the motor.
The TPS is a 3 lead device. One lead goes to the PCM neg return (not ground), one lead goes to the plus side supplied by the PCM (not the regualar battery supply), the third lead is the sensing feed back to the PCM that tells where the device is as a throttle angle indicator for all the above ways it signals the PCM for the various driving situations.
When testing voltage on the truck, test accross the leads only and not to ground or regular battery or you will get false incorrect readings.
Good luck.

 

okay so I think what your basicly saying is I tested it incorretly, I had an extra TPS from the other engine so I figured I'd just put it on anyways to save headache, the way I was testing it with a multimeter was on the actual wires with it plugged in, I was putting one lead on each wire and the other lead onto the block.....I guess that was wrong due to it being a full ciruit.....does it matter it its plugged in? or should I be disconnecting it and doing the test from thr front, and maybe from which connection to which? thanks

 

I'm taking your word on this and sayin F' it lol I'm cutting the wires off at the harness and bypassing the harness, brb to let you know that status, I can't wait any longer lol

 

To measure voltage, it must be plugged in with the ignition on.
The supply voltage comes from an isolated supply generated within the PCM that is 'floating' so there is no reference to ground.
When you see a "return" specified, it means the circuit is isolated.
The reason this is done is to prevent any possible interferance from other source signals.
There is another point that you may need to know that could cause the problem.
The cam position sensor , the intake air sensor, the cylinder head temp sensor and DPFE all share the same grey/red to the transmission and to the PCM.
There are other places the same lead is shared. What this means is a problem can be at another location and affects all the sensors operations because they are common.
The outputs from the sensors go to seperte PCM input pins to provide the information the PCM uses.
Look for damage, a short to chassis to a cross etc any where you done work.
I don't know how to make it simple for you except to look in Haynes book at the wire drawing to see where all the leads connect.

 

okay, I'm a tool....this motor/throttle body was from a van, guess I forgot to mention that lol. therefore the cable pulls flap opposite.....meaning there is two diff TPS for van and f150....******, I should have caught this one way sooner. anyways I have some wires to reconnect and alot of codes to reset,,,temp sen, intake, cylinderhead....blah blah just as you noted lol (damn, you know your ****) Also make sure to install TPS correctly......meaning it has to rollback 180 degrees before being screwed onto throttle body. Everything should be easy tomorrow now that this bug is gone.....PS I'm deff due to change oil now, should be like a partswasher now lol, Thanks Man

 

Your breaking into two different hardware configurations.
They work the same but must be wired to include all functions without leaving anything out.
Now you can see why there is more than one code set.

After all your are "back yard" re-engineering two different systems without benifit of previous experience.
Good luck.

 

sooo, I deff am gatting somewheres now, I'm getting much better throttle responds, to bad it stuck in 1st gear now lol, Idle is also stuck at 2000....the code came up as P1121. I'm guessing from testing and playing with the TPS either it's not springing back properly due to the spring being weak or I still maybe have installed it incorrectly, I didn't make it to the stealership in time today. I'll play with the TPs a lil more anyways