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Discussion Starter · #21 ·
The part to which that link goes, actually looks like the throttle position sensor that is mounted on the throttle body (butterfly), not on the throttle (gas pedal) pedal.

The picture is actually somewhat distorted and the female electrical connex appears a little too wide if memory assists me - which at my age, may not.

If so it's a feedback device to tell the computer where the throttle plate is in reference to the commanded position and if it is in parity to the actual position.
There are 2 Throttle Position Sensors (for redundancy) in this vehicle; the one you see, part of the pedal assy; and there is another one on the Throttle Body itself, under the hood (if I'm not mistaken.)

If one fails, the other one is supposed to take over.

Someone correct me if I'm wrong.
 

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There are 2 Throttle Position Sensors (for redundancy) in this vehicle; the one you see, part of the pedal assy; and there is another one on the Throttle Body itself, under the hood (if I'm not mistaken.)

If one fails, the other one is supposed to take over.

Someone correct me if I'm wrong.
OK ---- I don't follow that.

Let me lay down a rule for the sake of clarity ...

a) TPS is a Throttle Position Sensor, this being on the pedal assembly itself ...​
b) There is another TPS that senses where the throttle butterfly is ---- as in: OPEN or CLOSED (or shades in between) in concise resistance values that determine where he Throttle Motor moves the butterfly ... OK?​

First --- the protection factor is out if you have one TPS on the pedal and another TPS on the Throttle Body. They are important, but not a safety device.

What WAS needed - and I'm speaking of '02-'07 or so TB and Voys, etc., is that there are TWO potentiometers on the throttle pedal itself ............

One TPS starts at High resistance (Ω) and the other starts at Low resistance (Ω) and as the pedal is pushed, they both change resistance values.
One goes UP (let's call that value: "x") and ...
.... the other (herein called: "y") goes DOWN.

They both meet at a defined value where the x & y values cross.

If that position isn't met --- or there is "noise" on the surface of the pots and it changes the value outside of the designed-in parameters, then the SEL and REP lights fire up and you've got minimal throttle activity that will get you off the highway-road and you can creep at approx: 20 MPH to safety. <see note>

<note>
There's more to it than that blanket statement and I can go there later if you like - but right now I contend that there are at LEAST 3 sensors that are involved in Throttle Position Sensing and they all need to work together or codes will happen and flying monkeys ---- and wet witches ---- and ---



.
 

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a) TPS is a Throttle Position Sensor, this being on the pedal assembly itself ...​
b) There is another TPS that senses where the throttle butterfly is ---- as in: OPEN or CLOSED (or shades in between) in concise resistance values that determine where he Throttle Motor moves the butterfly ... OK?​
The one on the pedal is referred to as the "accelerator pedal position sensor". The pictures show it having 6 wires. That's enough for 2 independent pots.

 

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Discussion Starter · #24 ·
So, I changed the accelerator pedal with the sensor; and...nothing has changed. The CEL is still there with the exact same error codes (after I cleared it) and the same very randomly abrupt shift between 1st and 2nd is also still there. (I bought the connector as well but did not change it due to the electrical work involved; and I don't think it would make a difference.)

The 3 CEL codes are:

1) Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance
P0121

2) System Too Lean Bank 1
P0171

3) System Too Lean Bank 2
P0174

This is the LH6 V8, 5.3 ltr.

So what next? Go for the sensor in the throttle body itself? I feel like I'm just throwing $ at it, at the moment....
 

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Have you tried cleaning or changing out your MAF sensor? Also, check for vacuum leaks.
 

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So, I changed the accelerator pedal with the sensor; and...nothing has changed. The CEL is still there with the exact same error codes (after I cleared it) and the same very randomly abrupt shift between 1st and 2nd is also still there. (I bought the connector as well but did not change it due to the electrical work involved; and I don't think it would make a difference.)

The 3 CEL codes are:

1) Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance
P0121

2) System Too Lean Bank 1
P0171

3) System Too Lean Bank 2
P0174

This is the LH6 V8, 5.3 ltr.

So what next? Go for the sensor in the throttle body itself? I feel like I'm just throwing $ at it, at the moment....
With the info you've gotten so far, if you didn't test those devices before replacing them, you're getting ahead of the diagnosis here.

What were the High-Low values on the pots?​
What was their base voltage?​
Was there any chatter on their collective signals that made you replace them?​
Did you run the driving voltage pattern at the throttle motor ... checking for signal loss and voltage dropouts?​

Diagnose then replace. Yes you are throwing money away.

Do you have a digital meter and some 30ga backprobes?
 

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Have you tried cleaning or changing out your MAF sensor? Also, check for vacuum leaks.
That may be a good test .... but not yet. He/she has compliance issues first, with the throttle (and maybe themselves too).... THEN we can chase down the lean stuff.
 

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Discussion Starter · #28 ·
Have you tried cleaning or changing out your MAF sensor? Also, check for vacuum leaks.
Regarding MAF and vaccum leaks, Rockauto itself suggests:

Check for Vacuum Leaks First!

Vacuum leaks present symptoms similar to a faulty MAF Sensor. When replacing the MAF, always check for vacuum leaks, too. Common sources include:

Cracked or loose Vacuum Hoses / Connectors - an audio Stethoscope can help detect air induced sounds from vacuum leaks.
Leaking Intake Manifold Gasket (found in the "Engine" category) - Vacuum Gauge readings below 17-22 in-Hg (normal manifold vacuum at sea level) at idle may indicate an intake manifold gasket leak.
Note: As elevation increases, readings decrease. Subtract 1 in-Hg from normal manifold vacuum reference for every 1,000 feet increase in elevation above 2,000 feet.
Stuck open PCV Valve - remove the PCV Valve and gently shake it; if it does not rattle, the valve is clogged or dirty and should be replaced.
Cracked Intake Boot (found in the "Engine" category)
I'll have to have a friend of mine (more experienced) help me out with this.....
 

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Discussion Starter · #29 ·
With the info you've gotten so far, if you didn't test those devices before replacing them, you're getting ahead of the diagnosis here.

What were the High-Low values on the pots?​
What was their base voltage?​
Was there any chatter on their collective signals that made you replace them?​
Did you run the driving voltage pattern at the throttle motor ... checking for signal loss and voltage dropouts?​
I did not do any of these tests, unfortunately.

Diagnose then replace. Yes you are throwing money away.

Do you have a digital meter and some 30ga backprobes?
I do not. It's a bit above my pay grade, I should say. I'll check with one of my local friends more experienced and see what he says.

Otherwise, I might be able to get a local shop to do that (or something similar.) I will ask for details of what they actually propose to do in terms of diagnosis-- they quoted about $145, I believe, which is $ I'd like to avoid spending but might save me $, in the end. I can't really continue to throw $ at it (although I do get the parts for the $ spent.)

The truth is I'm more concerned about the abrupt shift (that it might be an actual transmission problem) than the CEL's and I'm not even sure they are related; but the CEL's started when this "abrupt" shift problem started as well....and I'm still thinking there's a chance they could be related.....
 

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If the abrupt shift is just the 1-2 shift, then it might be a crushed/broken cushion spring inside the 2-4 external servo. Maybe.

It might ALSO be from a bad metric from the throttle position/sensor/motor system - so cure the one problem first and you might be lucky.

I dunnow who or whom you can trust in a "shop" any more - and DON'T go near the dealer here they know little and charge a lot for experimenting on your dime.

You really need to learn these things if you are the owner of a vehicle that's out of factory warranty.

Fix it yourself or be prepared to launch crates of palletized greenbacks at the International Space Station.

There are LOTS of people here to help you, but you've gotta shove a dog into the fight --- a digital meter, a modicum of tools both Metric and US/B-S and a willingness to do it.
 

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Discussion Starter · #31 ·
If the abrupt shift is just the 1-2 shift, then it might be a crushed/broken cushion spring inside the 2-4 external servo. Maybe.

It might ALSO be from a bad metric from the throttle position/sensor/motor system - so cure the one problem first and you might be lucky.

I dunnow who or whom you can trust in a "shop" any more - and DON'T go near the dealer here they know little and charge a lot for experimenting on your dime.

You really need to learn these things if you are the owner of a vehicle that's out of factory warranty.

Fix it yourself or be prepared to launch crates of palletized greenbacks at the International Space Station.

There are LOTS of people here to help you, but you've gotta shove a dog into the fight --- a digital meter, a modicum of tools both Metric and US/B-S and a willingness to do it.
Couldn't agree more with everything you said.

On the abrupt shift, one thing to note is that it works as it should most of the time--and only randomly and infrequently does it do this weird (and very strong/violent) shift between 1st/2nd; if there was an actual mechanical problem such as the one you mention (crushed/broken cushion spring), wouldn't it do it all the time?

That's why I am still thinking or hoping that if could be a bad metric.

I will check with my friend and have him read this thread and see if he can help, has the tools, etc.

Will post back. Thanks.
 

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I've had instances of 2-4 servos failing from broken springs that did no damage to anything but itself... and had kinked pistons that ceased moving at all ... to springs that shattered and proceeded to grind huge scars in the bore ... which, unfortunately destroyed the case.

Some showed no shifting defects ... all the way up to those that chirped the tires every 1-2 shift.

There was no causal rule ... but not all of those failures manifested in bad shifts every time. Hopefully you don't have 2-4 servo spring scars inside the bore because that means a case replacement. It happens sometimes.

Good idea .... find a buddy ... but we might need tj and chem_man here for the computer stuff 'cause I'm more mechanically minded.
 

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Did you get the torque app yet? You can watch values for every sensor in the pcm and see if a value seems erratic.
I'm not connected to my truck so the pic is empty values but it just to show you an idea.
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Real time


Sent from my SM-G991U using Tapatalk
 

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Discussion Starter · #35 ·
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Thanks.

I have 3 OBD apps I can use, Torque isn't one of them unfortunately as not compatible, but I have:

AndrODB (useful and open source)

ODB Home (can't say I am completely comfortable with this app from China, not sure how long I will keep it but wanted to give it a try.)

Car Scanner (I quite like this one)

I can read various data live but it's hard (for me) to really know what to look for. I can isolate the MAF Airflow Rate, for example; and this app records as well so you can have access to the file even after your test drive, once you're disconnected. There is a 2.5 MB file from today for example, which you can read via the app, use various charts, etc., even when offline.

It'd be good to know what values and parameters to monitor.

I will also try to clean the MAF sensor, check for leaks, etc., next few days.
 

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In the last pics I sent, throttle position % is the actual throttle body on the engine (it will never be 0% at idle, it probably won't be 100% wide open) the throttle c and d or whatever it's called in the other picture is the dual axis potentiometers in the pedal as Mr.Montana pointed out to monitor for pedal sensor. You could have a bad wire to 1 of many sensors before you get there check and monitor the values.
The other codes sound like secondary 02 sensors. Either their not installed, if you have long tunes need to be turned off in the tune, or whatever reason but not your main focus. Get yourself the basic tools, DVOM (multimeter) jumper wires and a back probe kit, harbor freight prob $60-80 that will save you time and labor in the future (read, read, read) learn how to use the meter it's not too tough most sensors are either 2 wire 12v or 3 wire 5v but let's start slow.

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I also recommend that whenever anyone gets into Harbor Fright that they buy the $9.95 Logic Probe.

It's not terrifically intuitive, but once you break the ice with it, it'll be your go-to electrical/electronic test tool.

LINK HERE
 

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Discussion Starter · #38 ·
In the last pics I sent, throttle position % is the actual throttle body on the engine (it will never be 0% at idle, it probably won't be 100% wide open) the throttle c and d or whatever it's called in the other picture is the dual axis potentiometers in the pedal as Mr.Montana pointed out to monitor for pedal sensor. You could have a bad wire to 1 of many sensors before you get there check and monitor the values.
The other codes sound like secondary 02 sensors. Either their not installed, if you have long tunes need to be turned off in the tune, or whatever reason but not your main focus. Get yourself the basic tools, DVOM (multimeter) jumper wires and a back probe kit, harbor freight prob $60-80 that will save you time and labor in the future (read, read, read) learn how to use the meter it's not too tough most sensors are either 2 wire 12v or 3 wire 5v but let's start slow.

Sent from my SM-G991U using Tapatalk
So for the time being, I cleaned the MAF Sensor with MAF Sensor Cleaner and replaced the air filter which was filthy. You'd think that the shop I go to for oil changes would check that but I guess they didn't.
(and neither did I for that matter, until now.)

Seems to run slightly better now (possibly placebo effect).

For some odd reason, the CEL has not come back on for days now (I cleared it a few days prior to doing the above) and the abrupt shift between 1st and 2nd neither (yet.)
I imagine both of these (CEL + abrupt shift) will come back soon though....

(Another thing I have is that the voltage gauge is busted and for 6 months went all the way past the max voltage and got stuck there; I could see a spike using an ODB app but it would come back in range to normal values so I didn't worry about it. Strangely, possibly because of weather change, or something, it has come back in range now and just fluctuates within an acceptable range now, but it's definitely busted. The point here is: might it be sending the wrong values to the ECU thus screwing things up even more with incorrect values? I should think not.)

I'll try to find the same values you posted with the pics and see if anything looks weird. So far, I haven't noticed anything but will take more time to do it.

I'm still thinking the next "throw $ at it" step would be the actual TPS under the hood but it'd be good to "know before you go" as JoeMontana has said.
 

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Discussion Starter · #39 ·
I also recommend that whenever anyone gets into Harbor Fright that they buy the $9.95 Logic Probe.

It's not terrifically intuitive, but once you break the ice with it, it'll be your go-to electrical/electronic test tool.

LINK HERE
I can't go wrong for $9.95; I'll get it.
 

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Get a digital volt gauge and plug it into the cig lighter to monitor voltage or use the app when the gauge looks off to verify. I used a gauge in my lighter when I thought my alt was crapping out turned out to be the funky voltage measuring on the ground cable and everything was fine. Looked low on the gauge but never dropped below 13.2

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