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Tech heads enquire within please, tps problems 

 

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 Post subject: Tech heads enquire within please, tps problems
Posted: Tue Apr 14, 2009 5:11 pm 
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Hey guys.

Well after having some suspicions of a faulty tps, i did some testing on it today. Now, in the workshop manual specs in not only my EF manual, but the EB/D manual says the same, that at fully closed throttle the tps should have a resistance of 3000 ohms, and fully open it should have 500 ohms, approximatly. It also says when turned it should have smooth readings from one side to the other, which is obvious.

Anyway, i am getting smooth readings, and at 1 end and the other i am getting the 3000 and 500 ohm readings, except fot the major problem that the readings are at the opposite ends of the scale that they are supposed to be!! WTF?!?

So when i should have (by both the EB/D and EF manuals):
Fully closed = 3k ohms
Fully open = 500 ohms,

I actually have:
Fully closed = 500 ohms
Fully open = 3k ohms.

How can this be possible??
Was there ever a tps that was backwards and i somehow stumbled across it?

One would assume that 2 different workshop manuals on 2 different models printed years apart couldnt possibly both be typoed?

Andrew. :)

 

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 Post subject: Re: Tech heads enquire within please, tps problems
Posted: Tue Apr 14, 2009 5:22 pm 
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what about voltage readings?

at idle between 0.55-0.84 volts, and full throttle above 4 volts. I think the middle of the 3 wires you tap the multimeter in for positive, and the bottom wire for negative to test
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 Post subject: Re: Tech heads enquire within please, tps problems
Posted: Tue Apr 14, 2009 5:26 pm 
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your best off checking the voltage with the ignition on and see what the voltage is at closed throttle..
it should be 0.7v closed and 4.5v wot..
the tps specs are all the same from ea to el...
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 Post subject: Re: Tech heads enquire within please, tps problems
Posted: Tue Apr 14, 2009 5:49 pm 
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Ok i did that, and at closed i have flat 0.8v and wot i have 4.5v.

So i guess its ok then? Why is the resistance backwards? does that even matter then?

 

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 Post subject: Re: Tech heads enquire within please, tps problems
Posted: Tue Apr 14, 2009 5:54 pm 
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probably your multimeter leads backwards :lol:

 

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 Post subject: Re: Tech heads enquire within please, tps problems
Posted: Tue Apr 14, 2009 5:58 pm 
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Haha, nah i thought that too and tried it, but its not possible when simply checking resistance.

 

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 Post subject: Re: Tech heads enquire within please, tps problems
Posted: Wed Apr 15, 2009 2:54 pm 
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Easily explained. left pin to centre pin (wiper) 500 ohms. Right pin to centre pin 3000 ohms.
Move (rotate) wiper to other extreme. left pin to centre pin (wiper) 3000 ohms. Right pin to centre pin 500 ohms. It just depends on which end of the tps you referenced your multimeter to.

Resistance checks aren't polarity dependant so leads can go either way. Different story if you're testing diodes or transistors.

 

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 Post subject: Re: Tech heads enquire within please, tps problems
Posted: Wed Apr 15, 2009 3:27 pm 
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alfy12 wrote:
Easily explained. left pin to centre pin (wiper) 500 ohms. Right pin to centre pin 3000 ohms.
Move (rotate) wiper to other extreme. left pin to centre pin (wiper) 3000 ohms. Right pin to centre pin 500 ohms. It just depends on which end of the tps you referenced your multimeter to.



Good thoery but i tried this. Following both repair manuals and using the pins they specified still gave the backwards reading, while using the middle pin, and the opposing outer pin gave no reading. The 2 outer pins gave the manual specified 3350 ohms.

My tps seems to be in perfect order, but for some reason the ohms reading is backwards. Strange.

 

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 Post subject: Re: Tech heads enquire within please, tps problems
Posted: Wed Apr 15, 2009 5:49 pm 
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I'd suggest your manuals are wrong. Quick calc put the current flowing thru the tps at approx 1.5mA which means closed throttle at 500ohms = 0.75 volts. WOT which is 3000ohms or 350ohms from the end (based on your 3350ohms figure) is 5V (assuming your ecu logic is close to +5v) minus 525mv(voltage drop across the last 350ohms) = approx 4.5v.

All sounds sweet.

 

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