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Old Jun 5, 2008 | 03:05 PM
  #11  
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fraser9764
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From: Cheshire
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just read this in your old thread i found

PF01 - this is a variable resistor but with a switch in series with the wiper so that when the throttle is closed the output goes open circuit. The idea behind this is that the closed position is clearly defined. The sensor must be set up so the slightest movement will close the switch and the voltage will change from 5v to 4.4v.(the voltage decreases to 0.35v when the throttle is fully open). The disadvantage is that the most likely fault is an open circuit due to wear or a wiring problem, which cannot be identified by the ecu and so will not flag up a fault. A faulty output could cut the fuel during normal driving causing misfires or an engine which won't rev. The setting up of the switch position is critical as the throttle does not have to open very far for the revs to rise and the ecu must realize that it is the throttle controlling the revs and not the idle speed control valve, the result may be surges or stalling.

PF09 - This sensor is just a variable resistor and the extra programming capacity in the level 8 ecu is able to automatically calibrate the closed throttle position. The calibration takes place during normal driving by detecting the lowest stable voltage from the tps (which should be the closed position) and it then sets the threshold to that value plus a few millivolts. Because the voltage should never be 0v or 5v, unlike the PF01, then an error can be flagged up if they do to show a tps error and the program modified to ignore it. The tps is wired with the supplies reversed compared with the level1 / level6 so the voltage increases with throttle angle.


looks like both of yours ar fubard
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