Quote:
Originally Posted by knomadd
Vic, You may need to test that speed signal sending unit (whatever it's called) to see if it's even operational. I know it's new, but you know as well as I do, even some new parts are dead right out of the box. It sounds to me like you either have a dead sensor/sending unit, or a signal wire that's not hooked up correctly.
I'd think the trans software would show you the speed too, otherwise what good is it to be able to log data and see what it's doing before just blindly changing settings?
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I was thinking along the same lines, Duane. I called the GM Powertrain hotline this afternoon and discussed it with a tech. He said I should see a 1-3VAC signal right out of the sensor with the tires rotating. I need to get something rigged up where I can safely measure the sensor voltage with the truck in gear. Those pins on the sender are tiny!
The tech said if the sender was good, I need to hook a scanner to the OBDII port to see if the signal is making it to the ECU. It goes from the sender to the ECU and from there to the TCU. So if it makes it to the ECU and is readable at the diagnostic port, then I need to find out if it's getting in (and out of) the TCU. For that, I'll have to use the oscilloscope I have on order and don't have yet.
The tech was reluctantly helpful today. He said they were not really supposed to help consumers with diagnostics due to liability issues. But he gave me enough info to get me going.