what year and I guess a 4.3L? Vehicle is stock? no BS filters, chips, spacers. no other codes- any? Engine is reaching temp @195F?
This code is a rationality check for the mass air flow (MAF), manifold absolute pressure (MAP), and the throttle position (TP) sensors. Do you have a scanner that sees live data? If not - check for an air leak after the MAF, be sure the MAP has a good vacuum seal.