"As far as testing goes, when Bentley talks about 'To Test ECU Iimputs ', p241-7, is the test in step 7 different from using a voltmeter and looking for 0 volts ?"

Very good question. It is easy for me to recall the way this signal looked on the oscilloscope or suggest back-probing the ECU pin with a multimeter to determine its voltage, but totally impractical in the sense you need.

About the only thing I can suggest is, yes, test using the OBD inputs diagnostic. But test repeatedly, as if you are trying to catch it failing.

Envision a low voltage switch inside. The slightest few molecules of oxidation will interfere with contact, making "wipe" or self-cleaning much more important at low voltages. Think of a dirty switch and how it acts. You may have to stretch your memory back to the transistor radio days, or the on/off volume on that stock Volvo radio.

The diagnostic is going to report the slightest duration of successful contact, so it might say the switch is working if, just for a few milliseconds it did.

I say, yes do the test in the Bentley, OBD mode 2, but do it multiple times and look for consistency in results. Keep in mind how the LED works in response to the button press, as this is a better example of a "dirty" low voltage switch than I could have invented. Bosch's TPS should be a lot better, but the little O-ring doesn't keep out all the oil after years of service.

And backing off the hair trigger should help increase contact wipe.
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Art Benstein near Baltimore

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