95 4.3L Knock Sensor

Having a brain cramp...... I am going to be changing the knock sensors in a 95 Jimmy 4x4 automatic Vortec 4.3L W code. I seem to recall there are 2, one on each side of the engine. Question is do I need to drain the coolant because they thread into a water jacket? Or are they just threaded into a boss on the block?
Thanks for any info.

There is only one knock sensor. Remove the distributor and oil pressure sending unit for access to the knock sensor. No need to drain the cooling system.

Nope there are two, one on each side. RH side is just below the sparkplugs about mid engine, LH is just below the water temp sensor towards the rear of the engine. LH has an integral pigtail type harness and connector, RH just uses a connector.
I seem to recall the RH installs into the water jacket but can't remember for sure....... so when the truck shows up for the repair I guess I will find out if I should have drained the coolant or not :)

Thanks, I stand corrected. 96 and up use only one sensor.