Ok guys 2001 model here auto trans.  Yesterday on the way home pulling a small trailer coming into a small town about 60 or so.  Got a CEL and tach dropped and then picked back up.  I pulled over and did the key flip and got P1693.  I also have a superchips programmer I keep in the truck to read codes and plugged it in and I got nothing from it.  Cleared codes with it and continued on went 80 miles or so and it had never came back on.  Stopped to eat got back in and pretty quick after taking back off at lost speeds around side streets and parking lots it came back on.  10 miles later maybe stopped again and read codes again both ways again only had P1693.  Cleared again got back in and soon as I started it came on this time.  Got home about another 10-12 miles checked again.  Same thing only P1693.  Cleared again moved aroud the yard a little and put the trailer up and unhooked and it never came back on.  Tach went wacky every time when the light popped.  Everything I have read said the P1693 is just a companion code and something else should be showing but getting nothing else with reader.  Anybody have any ideas.  Thinking maybe came sensor but not sure.  Seems like I have changed it before but I don't remember. 

I just put an alternator on it maybe 6 months ago if that.  This is the first I'm hearing of a W-T ground mod.  I'll look it up. 

The can fail right out of the box for AC and most parts houses dont know what they are looking for when testing nor the level that is acceptable. WT's ground mod is in the articles section along with Mike's simplified version. A most worthwhile and simple modification.

Ran it up to the local shop this morning.  They confirmed no codes on it.  It was acting up again on the way there and back.  It's actually jumping up RPM not down.  First time it ever did it the tach dropped to zero and lost power now it's jumping up 100 RPM like it's in neutral for just a split second.  Some kind of a tranny sensor maybe?