toybota

Ok so here it goes. The other day im driving my truck and the dreaded check engine light pops on. I work at a local autozone so I pull the code with the trusty tester. It is a code 7 which is a TPS sensor. So I then disconnect the batt to see if it will go away out of curiosity. Of course it does not. So I do some poking around on here and find a link on how to "test" it. The test that I read just stated the value at idle and various points of space from the back stop. The issue I have with this is that once set properly for idle there is no adjustment for the other positions so what is the point of checking them? Well I get a new denso sensor from work and am about to install it and i realize I left the plug off the tps sensor. I plug it in and the light goes off instantly and the idle corrects itself from >2000rpm to <1000rpm. So my question is if the light does not come back on do you think it is ok now. I know parts don't just fix themselves but I also know that sometimes cars throw ghost codes that make the light come on. Once reset these ghost codes do not come back and the car functions properly. If the sensor is bad i would assume the car to re trip the light. If good I would assume it not to set the light off again. I say this because I know that on a ODBII car the light is reset after 3 times of starting the car. Any help would be greatly appreciated.

lonestar

I had a #7 code, and I believe the code is tps system error. Not only the tps sensor. I replaced mine and about twenty miles or so later the thing went right. that was a hard couple of miles though. I say don't mess with a good thing
good luck,
lonestar

ninjarunner

I had the same thing happen to my 4runner, it kept coming on and then going away later. i just replaced the sensor and have not had a problem in 2 yrs.

4Crawler

iTrader: (3)

Those tests are just that, to test that the TPS readings are correct. And you are correct, there is no adjustment for the overall tests. But the point of doing those is to verify you have an otherwise good TPS. IF it fails those tests, it is faulty and there is no need wasting time trying to adjust it. But if those tests pass, then you adjust the idle setting to make sure the TPS is installed properly:
- http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

And no need for a fancy "code reader" to pull the CEL codes:

- http://www.4crawler.com/4x4/CheapTri...CheckConnector

There are two basic types of check engine lights. One is set when some problem appears and a code is stored and then the light can go off if the problem goes away. Other problems light the CEL and it stays on. I think most are the first type, light is only on when the conditions are just right to trip the light. I get an O2 sensor light once or twice a year when 4 wheeling and doing long sections in idle. It'll come on and go off and that is it.

thook

Mind if I piggy back?.... (since I've had a TPS question or two in the back of my mind and didn't feel like starting a whole thread that would require a couple of simple answers.....)

Here goes..
A little while back I was testing the TPS on my '86 4rnr 22RE because of a low idle problem. I tested it and was off of the idle setting, of course.....read infinite. Question here is, how does a TPS go out of adjustment like this. I've never messed with it before.

Second thing, while I was resetting it, I noticed on the VTA-E2 "sweep" test that entails opening the throttle from close to WOT that the ohms would steadily increase and about midway through the range would drop momentarily only to increase again. It did this in a couple of spots. I remember reading on "cheaptricks" that this "could" be an indication that it is bad. So, I asked a mechanic I know and he suggested I try the same test using the volt function....as opposed to ohm....because he thought it is more accurate....not as "twitchy". [Roger} Do you think this is necessary at all? Or is the ohm test reliable enough to go by?

Another thing.....figuring it was bad even though it passed all the intitial tests, I reset the TPS (because I had no replacement on hand) and had to advance the timing by 2* to return it to 5*. Afterwards, the 4rnr began to hesitate...and still does....occasionally. Sometimes it seems to lose a little power on acceleration, also. But then, sometimes it's just great. Well, I know this behavior could be symptomatic of a bad TPS, but why in the hell would it start doing this only "after" I reset the timing and TPS and not before. I mean, if it's bad after testing then it was before, also. I'm guessing it might be something to do with the oil blow by in the intake and combustion "deadening" the fuel octane and is therefore manifesting because I had to advance the timing a bit, but I don't know....I'm just guessing.

One last thing...probably means nothing, but I'm curious. While I was running the VTA "sweep" test and found that little anomaly, I figured I'd do a little reading to try and understand what I was seeing. Well, I read that setting the IDL too close to infinite or open can cause certain operating behaviors and decided I'd set it as close to 2.3k ohms as I could get. I found that I could get values anywhere between infinite and 2.3k, BUT! even while I was holding the TPS completely still (even tightened one screw after a point) the meter would show that the TPS would not hold values greater than 2.3k. Can anyone explain why this is? What is happening here?

4Crawler

iTrader: (3)

The resistive strips on the circuit board inside the TPS can wear due to the sliding contacts that sense the throttle position. Or stuff like throttle body cleaner sprayed inside the throttle body can get inside the TPS and attack the delicate components inside.

Proper timing on the 22RE with an inoperative TPS IDLe-E2 contact is 12 BTDC instead of 5 BTDC. If you are running at 7, timing may be retarded too much.

I'll bet if you were to pop the cover off your TPS, you would see the resistive strip is worn or the sliding contacts are worn or dirty and you are seeing the results of this poor contact showing up in your meter readings.

thook

Hmmm.....well I reset the TPS BEFORE I even checked and/or readjusted the timing at all. And I didn't attempt to check or adjust the timing without the diag. term's jumped. In which case, the idle did drop supposedly indicating operation...no?

MudHippy

The idle dropped when you removed the the jumper wire from the diag. term's? Or when you jumped the term's with it?

thook

With the wire inserted into the diag. plug, the idle dropped. When I pulled the wire out, it jumped up again......all as "normal".

4Crawler

iTrader: (3)

That generally indicates it is working as designed. Was not clear on what you were saying regarding sequence of TPS adjustment and timing setting. And also, not sure on exactly how specific the <2300 ohms value is. Likely just an open collector input to the ECU and at some point, the resistance of the TPS IDLe circuit goes high enough that the ECU senses an off-idle condition. Might happen at 2301 ohms or 12,300 ohms or whatever. So maybe you were close enough to <2300 to make it work.

thook

I don't think this really explains what I saw on the sweep test between VTA and E2, though. If I may start over and hopefully explain myself more clearly.

Low idle problem began happening
Tested the TPS
Found the IDLe-E2 to be reading "infinite"....not where it should be
The twp others....VTA-E2 and Vcc-E2...were still within range
Then, I reset the IDLe-E2 to less than 2.3k ohms
Other two still within range
So, all looked fine and so check the timing (according to standard procedure)
Found it to be at 3*btdc, and so advanced it to 5*.....all done with ECU in base timing mode
Then, out of curiosity, I decided to run the VTA-E2 sweep as described on the 4crawler page:

"One final test, not listed in the FSM, would be to run the TPS shaft from idle to WOT and watch the VTA-E2 resistance and make sure it increases monotonically, no drop outs or dead spots. If you observe abrupt resistance changes, the TPS could have a burned area on one of the current tracks. See below for a detailed, step-by-step procedure for adjusting the TPS"

So, halfway through the sweep it drops out and then increases again....doing this twice.

Now, how can the TPS be showing propers resistance values according to FSM instructions, the ECU still go into base timing, yet the TPS fails this one little sweep test? And, I'm assuming this would be the cause of the hesitation?

TORTIS

iTrader: (1)

not to steal your thread here thook, hope your are doing well.

4Crawler did you invent the TPS? i ask because you seem to know this thing inside and out. my hat is off to you sir for your help on this and many other forums.

sorry to butt in. please continue.

thook

You rude man you! I say! [swat, swat!]

thook

Here's butting in for ya! (actually, I stole it first...hehehe)

4Crawler

iTrader: (3)

Why? Because the ECU never reads the overall TPS resistance. It is reading the VTA-E2 value as the throttle opens and closes to determine the throttle position (i.e. the throttle position sensor is how the ECU senses the throttle position). So if there are drop outs between idle and WOT, the ECU may see this as the throttle suddenly closing when it hits that spot. All the ECU can see is the resistance and when theat suddenlpy changes the ECU assumes something major has happened and adjusts the engine as needed.

So how can the end-end reading be OK and the sweep test fail? End to end resistance is just that, end to end on the resistive strip. The seep test uses the sliding contact to pick up the resistance in between the ends of the resistive strip. Someplace in the middle could be some dirt or something that causes the slider to lose contact or whatever and that can result in a drop out in the reading.

You can see the internal diagram posted above, those little sliding contacts ride on the resistive strips inside. Think of the inside like a tiny printed circuit board and the sliders move back and forth on the traces to pick up the signal. If there is a scratch or bump or whatever on the trace, the slider doesn't make contact and the reading changes abruptly.

thook

Thanks much, 4crawler. Makes perfect sense. So, it's safe then to pop the cover off to see if I can do anything...like cleaning it or something?

toybota

Ok so I retested the tps and I was testing the wrong terminals. So what i am saying is the tps tested good and the light was on. Upon replugging the tps sensor with the car running and check engine light on it now goes off. So would this make my tps sensor good? Should I try to pull off the back of the sensor and use some CRC mass air flow sensor to clean it? from my understanding it is just a variable resistor much like the indicator light for the fuel level. I know that the fuel one gets dirrty over time from varnish and can be cleaned to work after not working. can the same be done for the tps. I figure pop back of it off clean it out maybe just use a eraser. Get some rtv and put the back on? These things aren't cheap. I got mine from the zone for 65bucks but still hits my pocket. Im a poor student in my last year as a mechanical engineer. Thanks for the help.

MudHippy

If the light goes off when you plug it in, that's a good sign. Probably a good TPS.

You could run the sweep test if you still seem to be having some issues that might be related to the TPS. But, I'm of the same belief as you are when it comes to that. Pretty much a waste of time because if you set the IDL e2 correctly(RIGHT AT THE POINT WHERE THE OHMETER DEFLECTS WITH APPROPRIATE SIZE SHIM ON THE THROTTLE STOP), everything else should be set to go. If not then you shouldn't really be readjusting/rechecking it, as much as cleaning/replacing it. But, if your of the tweaker mentality, how can you resist I guess. (No pun intended) Pretty pointless though. It either works after you set it according to the FSM, or it don't. You don't need to reset or adjust anything after that to try to make it work.