Originally Posted by kerry

I don't think there are any scanners available which will provide that data. I have a 93 GMC 6.5 and all the forums indicate that the only way to get any info is from the original GM software program. There are aftermarket software programs available for 94+ GM OBDI vehicles.

MY TPS wasn't working right on my 93. (It sends a signal to the transmission control module). I discovered that the problem was a poor connection at the 'off' position. It always sits in that position and the connection deteriorates over time. I simply turned the adjustment on the TPS so the 'off' position was slightly different and it now works fine. This is a common problem on the 93 GM diesel truck TPS. Not sure about 89 gas models.