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TPS Voltage
Posted: Fri Jan 16, 2009 8:38 pm
by StuBeeDoo
Can anyone tell me the voltage output from an M20 (manual) TPS at WOT please?
TIA
Stuart.
Posted: Fri Jan 16, 2009 9:40 pm
by StuBeeDoo
Anyone?? I know I'm being impatient here, but I need to know for tomorrow morning.
Ta.
Re:
Posted: Fri Jan 16, 2009 11:14 pm
by case
Similar question. A lot of the guides mention a test for continuity, how do I do this, I have a multimeter but I don't know how to check, which setting do I use?
For Stu
Throttle Position Switch (TPS)
The TPS is mounted on the underside of the Throttle Body (TB) and tells the computer if the throttle is closed, partially open, or wide open (WOT). As the switch is mounted on the bottom of the TB, oil, fuel and other crud tends to find it’s way into it, causing it to fail eventually. When it fails, it results in erratic idle, higher fuel consumption or lack of power on WOT.First check if you hear an audible click when you fully close or open the throttle. If you don’t hear this, the switch is really shot, misaligned or somebody messed with the throttle stop.
If you hear it clicking, check if it actually works by disconnecting it’s connector and measuring continuity across it’s pins.
With the throttle closed there should be continuity between the inner and one of the outer pins
With the throttle partially open there should be no continuity between any of the pins
With the throttle fully open (about 7 degrees from it’s end) there should be continuity between the inner and the other of the outer pins
As a quick check if at least the idle switch is working you could disconnect the connector with the car idling. The idle speed should rise when you do this.
Re:
Posted: Fri Jan 16, 2009 11:21 pm
by Jon_Bmw
Stu, I don't know the voltage, but it is just a switch rather than a constantly vairable potentiometer(spel?) as seen in the 318is.
a 318is for example will read .2 when 20% open, and 0.6 when 60% open. (just examples, not hard facts.)
An m20 is either on or off IIRC, certainly on an m20b20 anyway... Hence its not that great for a Leonardo ECU that uses TPS as a one of the three sensors.
Re:
Posted: Sat Jan 17, 2009 12:14 am
by Brianmoooore
The TPS on all E30's except the iS consists of two switches (three if you include switchable autos). As such, it does not have an 'output voltage'.
The Leonardo has a software option for a TPS switch.
Posted: Sat Jan 17, 2009 9:19 am
by StuBeeDoo
OK, thanks everyone. 
Brian, I was hoping I could use the "full throttle" option on the Leo but I guess I can't. I'll just try increasing the "out of idle" range.
Re:
Posted: Sun Jan 18, 2009 10:28 pm
by johnlouis
The input the the TPS is actually 5v IIRC as the ECU generates 5v for all sensors to ensure it is not affected by battery voltage rise and fall (probably an 7805 or similar).
I was thinking about trying to create a small circuit that takes the idle and WOT signals from the switch and generates a 0v, 2.5v and 5v output for the leonardo so the WOT option could be used, but it is down the project list atm, though it should not be hard at all to do.
in fact it would be a piece of .... as the leonard has a high value input resistance, thus a diode or two and two resistors as a potential divider would be all that is needed.
you have me going now...
Re:
Posted: Sun Jan 18, 2009 10:50 pm
by Brianmoooore
The easiest way of setting things up for a Leonardo would be to fit a potentiometer type TPS (from a M42?).
I'm not sure what the petrol ECU would think of this signal. (Quite possibly it would equate 0V to the idle switch being closed, and anything above 0V to be idle switch open.) You wouldn't have the WOT signal, but you're not going to be running on petrol in any case, except in an emergency, if you have LPG