I finally am getting back into this problem.
from previous post:
Anyway I broke my foot had a baby and moved and now I think I can get back into this. I checked all the spark plug wires for resistance. They were all well within the suggested range which is below 25000 ohms they all tested from 600 to 1500 ohms. I started to manually check spark at the cylinders only got to two of them (so far, so good), but I rechecked the codes and now it is coming up with 272 and 274 I think. Anyway it was "Rich (bank1)" and "Rich (bank2)" do you suppose this is related or an entirely different beast. The truck: 99 Yukon 80,000.
Corey