TPS testing questions/clarification

redlinedeath · #1 04-23-2010, 05:15 PM

So im testing my tps, but dont know how to test it exactly on the multimiter. there are settings for 200, 2000 etc. i have the tps off the car already, any chance someone could give me a step by step instruction on testing it, and settings on the multimeter? any help is appreciated.

the cel came on, and that was one of the codes, so i cleaned it with some crc, and want to test it now. any help?

SoCal LS-L · #2 04-23-2010, 07:25 PM

http://www.subaru-svx.net/forum/showthread.php?t=53945

redlinedeath · #3 04-23-2010, 08:17 PM

no help, i understood all that. but i know what the numbers mean, so cool. heres what i got.

set at 20 k, with the test leads on middle and bottom(white and red) i got a reading of 5.42 im assuming thats 5420? am i wrong? right?
same leads, fully open reading of 0.09.

with leads on top and middle, it reads 0.36, fully open at 5.44

what do oyu all think?

the sweep across seemed ok, but i dont know for sure.

Trevor · #4 04-23-2010, 08:26 PM

Set your meter to a resistance in ohms scale covering up to 5,000 ohms.

ADJUSTING AND CLEANING THE THROTTLE POSITION SENSOR.

In order to adjust the TPS the manual says to measure voltage at the TPS by inserting meter probes into the plug at the ECU plug connection. In order to accomplish the feat at the TPS itself, therefore without tying yourself in a knot under the dash, you will require, best of all one of those dress making pins with a nice thin shank and a knob on the end, or a thin needle. Also a meter to measure 0.5 volts d.c..

The TPS comprises a potentiometer, incorporating a conductive plastic element, presumably used in a voltage divider configuration, as three wires come from it. There is a plug and socket close to the unit so that it can be easily removed for servicing. At this plug the wires are --- black ground and one end of the resistance element, red the other end and white the wiping contact.

Holding it with pliers, stick your pin/needle right through the white insulated wire, so that you can clip your meter lead onto it to make measurements. A fine pin will not damage the conductors as they will spread and there will be no significant damage to the insulation. Measure between the wiper, i.e. white wire and ground by connecting to the engine, or battery negative.

If you remove the unit, stick the pin in before replacing it, as it is much easier to do on the bench. Don't forget to pull it out when you have done the deed.

Now from the book :-- 1. Connect all connectors. 2. loosen TPS fixing screws. 3. Turn ignition on. 4. Adjust TPS position, (i.e. rotate the complete assembly), while throttle valve is confirmed FULLY closed, to specified voltage, using a volt meter. 5. tighten fixing screws.

The voltage is specified as within a tolerance of from 0.45 to 0.55 volts. You should have no trouble in setting things at exactly half a volt.

Before removing the TPS or altering the original setting it is a good idea to mark the mating castings with a scratch so that one can check on the adjustment, before and after, as a matter of interest. It is always nice to know if the effort expended has in fact improved things.

CLEANING AND CHECKING.

If the unit is removed, it is easily checked with an ohm meter for smooth operation or otherwise. Evan without dismantling the unit a spray with CRC or similar cleaner and a work out will do wonders. The resistance end to end ( black to red ) should measure very close to 5000 ohms. Measuring between white and red or black should show a smooooooth change in resistance when moving the control shaft over full distance. Blips will indicate trouble.

With the unit in place, a voltage check on the output as the mechanism it is operated while connected and energised, will also give an indication of possible intermittent contact. Again using a needle or pin to make a connection can be helpful. A smooth change in voltage should be recorded.
A meter with a bar graph will show up short duration faults much better than a normal instrument, digital or analogue, as both have an inherent time delay before indication is registered. This factor should be taken into account but should not deter those without sophisticated gear.

redlinedeath · #5 04-23-2010, 08:52 PM

my settings let me do 200, 2k, 20k and higher. is 20k good? while im doing the sweet from 5.44 dowm, thewhole and tenths place decimals are pretty smooth, but the hundreths place is jumpy, even when slow, is that normal for me turning itby hand? also, when i have it in the car and set it, do i do it on the ohms setting? or the setting that reads DCV?

processengr · #6 04-23-2010, 09:34 PM

Quote:

Originally Posted by redlinedeath

my settings let me do 200, 2k, 20k and higher. is 20k good? while im doing the sweet from 5.44 dowm, thewhole and tenths place decimals are pretty smooth, but the hundreths place is jumpy, even when slow, is that normal for me turning itby hand? also, when i have it in the car and set it, do i do it on the ohms setting? or the setting that reads DCV?

Set the meter to VDC. Adjust to .5 vdc range is .45 vdc to .55 vdc. I defer to Trevor to confirm.

Trevor · #7 04-23-2010, 09:39 PM

Quote:

Originally Posted by redlinedeath

my settings let me do 200, 2k, 20k and higher. is 20k good? while im doing the sweet from 5.44 dowm, thewhole and tenths place decimals are pretty smooth, but the hundreths place is jumpy, even when slow, is that normal for me turning itby hand? also, when i have it in the car and set it, do i do it on the ohms setting? or the setting that reads DCV?

Yes, use the 20K range i.e. 0 - 20,000 ohms.

The measurement should be smooth throughout, up to 5,000 ohms. Not sure what you mean by --- "the hundredths place even when slow". You are looking for poor contact as the moving contact passes a set distance and you must turn the shaft slowly. Read the above data in full so that you understand what is involved.

An intermittent contact at the high ohms end of a reading when this is taken from red to black connections, will be of less importance than one at the low ohms end, which will equate with low throttle positions and involves take off and low speed control. Even so any intermittent contact is not a good thing.

It is very important that the reading across the complete resistance i.e. from red to black reads a stable approximately 5,000 ohms, no matter how you bump the unit about

Trevor · #8 04-23-2010, 09:44 PM

Quote:

Originally Posted by redlinedeath

my settings let me do 200, 2k, 20k and higher. is 20k good? while im doing the sweet from 5.44 dowm, thewhole and tenths place decimals are pretty smooth, but the hundreths place is jumpy, even when slow, is that normal for me turning itby hand? also, when i have it in the car and set it, do i do it on the ohms setting? or the setting that reads DCV?

Yes, use the 20K range i.e. 0 - 20,000 ohms.

P.S. When setting the TPS use your 2 volt DC range or whatever is closest.

redlinedeath · #9 04-23-2010, 09:55 PM

thank you agian, youve been alot of help lately!

so ive done the test a few times, and confirmed with my room mate, there are a couple spots where the smooth numberchanges jumps. i guess it may be bad after all. ill find out when i get it back on the car and bolt the driveshaft and exhaust back up.

Trevor · #10 04-23-2010, 11:38 PM

Quote:

Originally Posted by redlinedeath

thank you agian, youve been alot of help lately!

so ive done the test a few times, and confirmed with my room mate, there are a couple spots where the smooth numberchanges jumps. i guess it may be bad after all. ill find out when i get it back on the car and bolt the driveshaft and exhaust back up.

As mentioned in the data above. --- Evan without dismantling the unit a spray with CRC or similar cleaner and a work out will do wonders. Try working it into the innards as you move the shaft back and forwards, then test again.

redlinedeath · #11 04-24-2010, 07:10 AM

i did that before i tested it. i really wish i would have tested it before i cleaned it to though for a reference on the readings.

Austin · #12 05-30-2011, 09:41 PM

So looking back at this thread, I'm not sure what I'm doing when I try this stuff. I found the TPS, marked it and the throttle body so I could match 'em back up, stuck the needle through the white wire and alligator clamped it to the positive lead on my multimeter, connected the negative lead of my multimeter to my negative battery post. Then I turned the car's ignition to the "on" position.

I had the multimeter set to 20V (since I could register the battery's 12.55 volts in that range, obviously I should be able to register .5 volts). It registered zero. I moved the throttle back and forth and got nothing. So I thought, "okay maybe by 'on' they meant 'cranked'.", so I started the car. Still nothing.

So obviously I'm hooking something up wrong. Does the ECU have to be plugged in a certain way? (I ask because many tests on the XT6 require the built in test connectors on the ECU to be either connected or not.)

I am trying to test/adjust my TPS because my 4EAT is shifting between 3rd and 4th constantly. Just in case, I removed the TPS and sprayed CRC contact cleaner inside as best I could and worked the spring mechanism back and forth. Not much came out except a barely noticeable few white flakes, which I assume were a bit of corrosion.

When I reattached the TPS and took it out for a drive it didn't seem to have made any difference at all.

Any tips? Am I hooking it up wrong?

oab_au · #13 05-30-2011, 10:10 PM

Quote:

Originally Posted by Austin

So looking back at this thread, I'm not sure what I'm doing when I try this stuff. I found the TPS, marked it and the throttle body so I could match 'em back up, stuck the needle through the white wire and alligator clamped it to the positive lead on my multimeter, connected the negative lead of my multimeter to my negative battery post. Then I turned the car's ignition to the "on" position.

I had the multimeter set to 20V (since I could register the battery's 12.55 volts in that range, obviously I should be able to register .5 volts). It registered zero. I moved the throttle back and forth and got nothing. So I thought, "okay maybe by 'on' they meant 'cranked'.", so I started the car. Still nothing.

So obviously I'm hooking something up wrong. Does the ECU have to be plugged in a certain way? (I ask because many tests on the XT6 require the built in test connectors on the ECU to be either connected or not.)

I am trying to test/adjust my TPS because my 4EAT is shifting between 3rd and 4th constantly. Just in case, I removed the TPS and sprayed CRC contact cleaner inside as best I could and worked the spring mechanism back and forth. Not much came out except a barely noticeable few white flakes, which I assume were a bit of corrosion.

When I reattached the TPS and took it out for a drive it didn't seem to have made any difference at all.

Any tips? Am I hooking it up wrong?

The negative should be connected to the at the TPS, to set it right. Connecting it to the battery can incluide a lot of other resistances, that will be incluided in the 0.5V reading.

Harvey.

Austin · #14 06-03-2011, 10:04 AM

Quote:

Originally Posted by oab_au

The negative should be connected to the at the TPS...

Harvey.

What is the "AT"? You don't mean the transmission do you? Like grounding it on the bell housing or something?

---Edit---

Wait a minute - I guess that was maybe a typo? So you mean I just need to connect the negative lead from the multimeter to the TPS - I'm guessing the black wire then?

oab_au · #15 06-04-2011, 05:20 PM

Quote:

Originally Posted by Austin

What is the "AT"? You don't mean the transmission do you? Like grounding it on the bell housing or something?

---Edit---

Wait a minute - I guess that was maybe a typo? So you mean I just need to connect the negative lead from the multimeter to the TPS - I'm guessing the black wire then?

Yes that was a typo. Take the reading across the TPS. Pos on the white, Neg on the black.

Harvey.