99 Rodeo P1647 code.......need some help here

Hello, a freind of mine has a 99 rodeo, base model 4cyl 5 speed, that has an intermittent CEL and i pulled code P1647 that said manufacturer code aux input aux output.

I have looked up code list for isuzu online and this code isnt listed, so im kinda wondering what it means. I went ahead and erased the code for now to see how fast or if it even comes back.

Truck only has 80K miles and runs fine otherwise.


I really appreciate the help here.