Ya dude, there is some way to pull the codes on your truck, I am not familiar with 2nd gens, but I think they need to be extracted with a scan tool.

In other words, when the engine computer, or ECM, computes values that it feels are representative of malfunction, it will store a code (like 5 digit number) in the computer that can be extracted with a special hand-held machine which plugs into it. The codes represent different errors.

For first generation isuzu's before 93 (approx) getting the codes can be done at home, I think for 2nd gens you need to go to a dealer.

Post up here what you find, and welcome to the board.