I have a 2004 Silverado 1500 extended cab 2x4 with the 4.8L V8 engine After driving through some serious flooding I starting getting an intermittent check engine light that turned into a stay on engine light. I went to advanced auto and had them pull the code... it was the #2 knock sensor. I pulled the truck apart finding water in everything from the airbox to the intake and finally the #2 knock sensor that was completely submerged and rusty. I changed both knock sensors, changed the oil and transmission fluid. The light went away for a week or two then came back the codes still saying #2 Knock senor... I have heard a mass airflow sensor could be the culpret. before I spend anymore time and money chasing electrical issues I was hoping to find some answers... The local dealer has been consistent in making all repairs there thus far cost a minimum of 1000.00 usually requiring 2 or 3 trips to get it right so I like to avoid them if I can any ideas?