Throttle position sensor/circuitry checking w/resp. to poor fuel econ.

[Ameer Antar]

I would check the wire that carries the voltage to the pins for excess resistance. Just b/c the wires look OK doesn't mean they're fine. Corrosion can affect copper a great deal especially under the hood where the insulation might melt due to heat. Also, you might want to check your multimeter for accuracy by testing it w/ some voltage you know is correct, such as the battery, etc. To measure the resistance of the wires going to the TPS, first get a length of wire or alligator clips to reach from the beginning and end points (ie. ECU and TPS connector). Measure the resistance of the additional wiring alone before measuring the wires from the harness. This will value will be subtracted to zero-out any resistance in the testing leads and additional alligator clips, much like zeroing-out the mass of a container to measure the mass of a liquid. Then, make sure no power is going through the wires (otherwise you will get false readings) and test the resistance of both the positive and ground wires from the harness. Don't forget to subtract the resistance of the test leads. I would imagine the resistance should be less than half an ohm, but the Bentley may have a spec. At about 0.5 ohms the wire will drop the voltage from 5.3V to 3.3V, assuming a current of 250 mA. The more the current flowing through the wires, the larger the voltage drop and the same w/ resistance. This is from Ohm's Law: V=IR. At least this way you can rule out the wire's fault and move onto other possibilities. Good luck.

-Ameer

>One of the suspects I've been trying to rule in/out is the throttle position sensor and circuitry.
>According to Audi/Bentley Sec 24-120-2 the voltage between pins 1 and 3 must be 4.5 to 5.5
>volts. On my car the reading was 3.3V. According to Bentley that means faulty wiring or bad ECU.