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Old 06-13-2013, 12:03 PM   #1
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Hi guys!

So I recently got this VTPS sensor off a FIAT, which is nearly plug and play on the engine loom.

I connected it to see if it worked, and noticed that it works in a reverse way than it is supposed to: When the throttle is shut, the ADC reads around 200, and when the throttle is fully open, ir reads around 20.

Despite the warning that the WOT ADC was less than the throttle shut ADC, Tunerstudio seems to have taken the calibration quite well, and the throttle scale shows correctly (0% when off the throttle, going to 100% when at WOT). But then I noticed this will impair some functionality, such as the overrun fuel cutoff feature, which works only below a certain amount of raw ADC.

Seeing as the ADC reduces as the throttle opens, I basically lose that feature (well, I never had it in the first place before, so I guess I don't lose that much)... I suppose the TPSdot enrichments table will also have to be sort of reversed, as it is based in Volts/s.

So, the question is, can I get this functionality back? I read somewhere that when you get a reverse reading, it means the GND and +5V wires have been reversed when connecting the VTPS. Haven't tried it, as I'm lead to believe by the datasheet on a similar sensor that mine has been wired properly, so if I try this, can I possibly damage the sensor?

Cheers guys.
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Old 06-13-2013, 12:06 PM   #2
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reverse your ground and 5vref wires.
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Old 06-13-2013, 12:07 PM   #3
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So that shouldn't cause any damage then? I will give it a try right away

Thanks brain!
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Old 06-14-2013, 05:27 PM   #4
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No harm will be done to the tps or the megasquirt.

What tps exactly are you using and what did you have to modify?
I'd like to add the information to the vtps thread here.
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Old 06-14-2013, 05:30 PM   #5
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It is a Punto GT VTPS. I'll gladly take some photos for you once I get a spacer manufactured, it's not quite plug and play:



It fits the pivot, and you can adjust it to the throttle travel area, though the bolts will not match and the sensor itself will stick about half an inch away from the mounting surface. I'll be making the spacer tomorrow.

Inverting the polarity did work, perfectly
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Old 06-15-2013, 01:02 PM   #6
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As promised:



Ended up inverting the red and black/green wires in the connector instead of messing with the engine loom again. It works perfectly now. In the position I mounted it, reads 25~220 ADC.

Spacer total width is about 10mm. I made it a two-piece so I could adjust the position if needed. Working great for me
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