I took the truck out for a run (first time in months, it was down for a fuel pump replacement) and got a code 51 after about 6 minutes of driving. No flashing SES, however. Just solid. No driveability issues and I stopped and pulled the code by shorting the ALDL pins. (I didn't have my Windoze laptop with me.)

I returned home without clearing the code. When I went WOT, I thought I heard distinct engine knock, so I backed off. Otherwise, the engine performed fine.

I am using the G3 switching adapter with the remote switcher. I only loaded up 4 bins and stacked them. This is the same chip I had in there months ago. No changes. And I know I didn't accidentally switch the bins. I've switched bins to an empty "slot" before and I got a flashing SES.

I reset the computer when I got home and unplugged the remote switcher and will try using the on-board knob tomorrow.

Any ideas?