Hello all, - I searched the forums for this issue and got a little bit of info but not any exact info about this......
I have a 96 LS 3.1- I did a oil/filter change today and for the first time I noticed 2, what appear to be sensors on the front side of the engine block below the exhuast manifold. I looked at my haynes and I approximate they are knock sensors. Ok, question 1, the book says that the 3.1 has one below the ex-manifold/ above the oil filter. Ok(and the pic looks different than what I got) ....so it (the haynes) also goes on to say that the 3.8 has another sensor located on the backside of the block. I have 2 sensors on the front of the block in the described locations. Is 1 of them the knock sensor and the other a different sensor? Do i have some weird engine rebuild? Now part 2 to my question, both of the sensors have cut wires, meaning there is about and inch of sheilded wiring hanging off the sensors but as you can figure they arent hooked up to anything,???? just 2 sensors on the block going to nowhere. I do have a slight knock BTW. thanks.

 

The left sensor is the knock sensor and the right one is the oil pressure switch. Does the slight knock go away when it warms up a little? If so that is a extremely common condition called "piston slap" it's none damaging and hurts nothing. Try using synthetic 5w30 oil it really made the difference in my 95 grand am with a 3.1

The red oil light should be on if the pressure switch isn't connected at all though..??

 

well, I went and looked at the wiring diagram and there is knock sensor #1 and #2 running to the PCM. light blue and dark blue wires on the 3.1 96 although the book says otherwise in the emissions chapter ( which we all know the book sometimes isnt exactly right). I had the knock come about this winter and it was more noticable during initial start-up. I hadnt noticed it recently until I changed the oil today. Its been running fine, as most montes do, no warning lights at all.So I guess the real question now is do I need to worry about it and get it repaired, guess it'd be costly since it involes the PCM.

 

Under hood, center, front engine area, below exhaust manifold, mounted on block

 

yeah, I said where it is located and know what it looks like, thanks anyway.

 

If the knock sensor is not connected it will have a hard time when under load to not have engine knock. However if the rear KS is working it should pick that up. My worry is that the engine has low oil pressure and someone removed the bulb from the IP for the oil light. If the wiring is correct and the oil pressure sensor is not connected a red light that would indicate low oil pressure will be on constantly