Winter held on a lot longer this year than I have ever seen before in New England. Temps are finally starting to climb out of the 30s so I'm going to get back on track diagnosing the van's trans/ABS/speedo problem. Sorry to bring this topic back from the dead...

Let me preface this by saying that I have driven the van maybe 6 or 7 times since the last time I took on this issue, just to move it around and run a couple very short moving errands in the neighborhood (where I knew I wouldn't need more than ~20mph out of it). I'd say that it was almost exactly a 50% chance, over that period of time, of whether the speedo would work and the trans would shift. Some of the time it worked flawlessly, other times, it did not work at all. One time it start out fine, then after I got to where we were going and turned it off for 5 minutes to unload it, it stopped working right. It is hard for me to imagine what would be the determining factor in making it work or not work. There was no pattern related to temperature, humidity, time since last run, etc. Whether or not it worked was just completely unpredictable. I am about to go get it from where it is parked and bring it home to work on it, so we'll see what it does today.

On the occasions when it does not work, no amount of fiddling with the ignition switch will make it quit acting up. Is there anything I can do to test the switch?

I got under the truck back a few weeks ago to poke around and discovered there are many sensors and plugs towards the back of the trans. Which is the VSS one? What side of the trans is it on? Also, if this were a grounding issue in a location different than that sensor, where would the loose ground be? Just at the battery terminals, engine block etc? Sorry for my ignorance -- this is my first time dealing with an electronically-controlled automatic, and first GM vehicle.

I guess my plan today will be to do the ALDL procedure and see what code it is that it's been throwing when that ABS light comes on, probe around for gummed-up connections at the sensor or loose/corroded grounds, and see where that takes me.

Would appreciate any opinions or advice. Thanks again for all the help on this issue.