Help with 3B TPS measurement

[newsh]

I need some help please guys, I want to check my TPS measurement against someone elses to see if I need to get a new one.

I need the Measurement in Ohms between Pins 1-2, 2-3 and 1-3 with closed throttle and then again at WOT using the loud pedal. The connector from the loom should be unplugged.

If we could get readings from a couple of cars to see a trend that would be great.

Thanks

[twoqu]

John,
The published figures are:
With throttle closed:
Between terminals 1 & 2 1500-2600 ohms
Between terminals 2 & 3 750-1300 ohms.
Then open the throttle and the resistance should increase to a max of 3600 ohms between 2 & 3.

Although recently 220BHP got those readings but it was only when he replaced his TPS with a good s/h one did his problems disappear. The TPS had a dead idle circuit switch mind!

http://www.s2forum.com/forum/showthread.php?t=17795

[porkkis]

Again. Don't measure resistance. Measure output voltage.

[newsh]

I get 900 on the pins that dont change and a max of 2700 Ohms at WOT.

Porkis, thanks, I'll try and do the output voltage test tomorrow, I have this strange thing where if I open the throttle to the stop I get a reduction in boost so I've had to loosen the cable so it stops a few degrees before WOT. Really weird.

I've also had this thing where the temp and fuel gauges readings change, eg. one minute it reads 1/2 a tank and the next minute 1/4 of a tank. Like there's a voltage regulator going bad somewhere. I can't see the ECU using the same voltage reg as the Fuel and temp gauges though.

[twoqu]

Hmmm..
I get 970 and 2770! Althought this TPS is off the car. No guarantee it functions correctly. Think Lou measured 3600 which is what i was led to believe was the correct figure at WOT. See here also:

http://www.sjmautotechnik.com/trouble_shooting/20vthrot.html

[porkkis]

Oh dear. Please stop talking about those resistances. The internal resistances of a potentiometer may vary and it still gives the same output voltage. ECU sees only this voltage so that's what should be measured and nothing else. This also means that same part number TPS may have different potentiometers inside.

I would very much appreciate if s2central would also document this on his website and absolutely nothing about the pot. resistances.

Newsh, your TPS is most likely faulty. Simply too worn so that the contact breaks at WOT position. The output voltage probably drops to 0 at WOT. It should raise from near 0 to near 5 volts. About 0.2 to 4.8 is ok.

[newsh]

Ok Porkkis, I understand now you say it like that, of course in pure voltage terms the potentiometer will just fade between 0 and 5 volts no matter what its resistance. I'll do the voltage check and probably get a new unit anyway, its done 200,000 miles after all.

[jameswkr]

My TPS also "fails" the resistance test. Which pin is output voltage ? I assume you measure with ignition on with the boot over the TPS connector pulled away ? My car also seems to pull better if I back off from full throttle...

[Greg_S]

I also have an issue with my TPS i think. Sometime when I lift off to stop at a junction the car stalls, was bringing up an error code on vagcom for it so its prob worth replacing in the near future

[newsh]

Measure between pins 2 and 3 with the ign on and the boot pulled back. Mine measures ok, just above zero to just below 5V. It then occurs to me that the connector is the same type as the MAF, low pressure contacts, so that will get another good clean. I used a moving coil "analogue" meter so I could see that the voltage change was smooth.

[jameswkr]

Thanks newsh. Something to do after lunch now I (think) Ive fixed the water leak on a rear light cluster....

[newsh]

I just rechecked the measurement using the accelerator pedal, my throttle cable is now adjusted to give 4 Volts max. Any more than this the ECU starts to cut boost.

[Greg_S]

Are you getting the right boost again now?

[newsh]

Are you getting the right boost again now?

Yes, I get at least 26psi at 3k dropping off gradually after 4k.

If I let the throttle go all the way to the end I only get 20psi at best. (Unless I lift off slightly in which case the boost comes up and the car surges forwards)

[jameswkr]

FWIW, my voltage output goes from 0.34 to 4.65.