Engine knock is something you cant hear most of the time under light acceleration. The 05's and 06's have the knock sensors. The 04's don't. The knock sensor can read up to 1.2 volts before the timing is retarded 2 degrees. Don't know what the normal knock sensor voltage is at under ideal torque and HP curve but I assume it's around the 2500 - 3000 rpm range. Can someone data log the knock sensor voltage going 35mph in 6th just cruising and also going 35 - 50mph under light acceleration. The voltage reading should end this debate.