Take a voltage measurement right at the sensor, then compare that to what is being shown on the scanner's live data screen. There's mechanical stops in the throttle position sensor that limit its range of signal voltage to approximately 0.5 volts at idle and 4.5 volts at wide-open-throttle. If the 5.0 volt supply is good, and you find 0.2 volts on the ground terminal, you must have 0.5 to 4.5 volts on the signal terminal unless there's a bad connection on one of those first two terminals or the sensor has a break inside it. A break inside is very rare.
If you find the proper voltages on the signal terminal, (by the way, those measurements are only valid when the sensor is plugged in, so you have to poke through the rubber weather-pack seals to take the voltage readings), but the scanner shows 5.0 volts for "TPS voltage", there's a break in that signal wire. Due to the internal interconnected circuitry inside the Engine Computer, a break in the TPS signal wire could allow the signal voltage to "float" to some random value. That random value could be within the acceptable range of 0.5 to 4.5 volts, then the computer would accept it and try to run on it. To prevent that and to force a defective condition to be detected, a "pull-up" resistor is added to put 5.0 volts on the signal wire. That will result in the computer setting the fault code, "TPS voltage too high". If there are no TPS-related fault codes, the sensor is working properly.
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Friday, December 11th, 2015 AT 1:46 PM
