So here's what I learned from my afternoon of wrenching on my '99 Blazer trying to solve a P0327 code. Hopefully this is helpful to anyone else who may need to deal with their knock sensor.

1. Remove the negative battery terminal cable. Do it right or don't do it at all.

2. The items that MUST be removed to access the knock sensor include the distributor cap and plug wires, the brake booster vacuum line, and as many of the various vacuum lines and wiring looms nearby. Get as many things out of the way as possible because access is limited. I did NOT remove any fuel lines nor did I remove the entire distributor assembly. EDIT:In my quest to now replace my intake manifold gaskets (new project), I've found that the fuel lines aren't as difficult to remove as I thought. I definitely recommend removing them now. There are two flare nuts behind the little wing bracket that you can get to with a 16mm crow foot wrench. Or a stubby 16mm. Do yourself a favor and remove the fuel lines. The pressure relief valve is right there and it's a total of the two nuts plus one 10mm bracket bolt to remove, then lift (or very gently pry) out of the injector. This will save you an hour or two of trying to remove/replace your knock sensor and the associated connector using one fingertip.

3. I accessed the general area of the knock sensor from the driver's side first, but worked from both sides on a small step stool the whole time. Stretch your hammies and lower back, because all of this stretching and reaching is a workout. Get some small LED worklights to use against the firewall, it makes a world of difference being able to see. I also use a headlamp, but those extra battery powered led lights made a big difference.

4. The plug/connector on the knock sensor can be rotated while still attached. It's almost directly below the fuel lines on the driver's side of the distributor cap and can be difficult to see without those lights mentioned above. To disconnect, you have to squeeze two sides and lift, but there's not enough room to get two fingers on the connector. From the passenger side, I had my left hand against the firewall on the back side of the connector pushing one side while I used a long flatblade screwdriver against the front side of the connector. Can't fit two hands down there, so one hand plus a screwdriver is what it takes to remove the connector. There are small square-ish points on two sides of the connector that you press that should be visible thru the fuel lines. Rotate it and use those lights until you see what you need to work against. Edit: if you remove the fuel lines, access is way-easier and will save time.

5. Once the connector is removed, pull it out of the way around the back of the distributor. It can't fall too far, but it'll get right in the damn way if you don't secure it.

6. Next is getting the sensor removed. I fished a standard (shallow) 7/8" socket from the passenger side under the fuel lines and onto the sensor. Just the socket. Once it's on the sensor it's not going anywhere, so I then moved to the drivers side and fished a wobble extension down thru the fuel lines. I used another 6" extension just to get the ratchet enough length to operate. There's enough access for a 3/8" drive socket and wobble extension between the fuel lines, not sure if a 1/2" system would work. I connected the wobble extension to the socket and moved back to the passenger side to hold the socket as squarely on the top of the sensor as possible. My wobble only allows about 15-degrees of rotation, so it was close. The socket wanted to rotate off of the sensor, but with enough patience you can get it loose.

7. Once the sensor is loose, it'll come the rest of the way out by hand. Remove your socket and wobble extensions and unscrew the sensor. Celebrate with your beverage of choice.

8. Check distributor cap and rotor - mine had some corrosion and heavy pitting on the contacts so those are getting replaced along with the sensor.

9. Re-assemble in reverse order. Easily said, but also difficult in reverse. I still think disassembly is the harder part, figuring out how to get access and whatnot.

Hope this is helpful. This info would have saved me time, so I thought it would be useful to post.

 

Wow. This is great! Thanks for posting!

 

This sounds like the oil pressure sensor/sender. I thought the knock sensor was low on the block, about in the middle front to back, screws into the block coolant jacket.
Now I am going to have to go look.

 

At some point (I don't know exactly what year), it moved up to the back of the block near the oil pressure sender.

 

Interesting that they moved it. At least it's not under the head or anything crazy. This image shows a view from behind the firewall looking forward. What's not shown are the fuel lines that run over the top, but the knock sensor is item 3.

 

And so it is!.....how about that....learned something new and it's only Monday morning.