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Hello. I have a 2004 silverado with the 5.3l vortec. Check engine light is on with code P0327 (knock sensor 1 circuit low). Before I take off the intake and replace it, I was wondering if someone could tell me what steps to do to verify it's the actual sensor itself and not something else. I've read several forums where people replaced both sensors and wiring harness and that not fixing the issue. So far all I've done is unplugged the wiring harness and doing an ohm test from the side of the harness that runs to each knock sensor. I dont remember exactly which one was what, but 1 of them was at approximately 102 ohm and the other was approximately 101 ohms. I haven't pulled the ecm yet to check if theres a short in one of the wires that come from it to where it plugs into the knock sensor harness. I dont want to replace both sensors and the wiring harness and it not solve the issue. Also, from what I read I heard it is imperative to use only ACdelco knock sensors as other aftermarket ones wont read or work correctly. Any advice on what I can and should do to make sure it's the sensor itself would be greatly appreciated. Also, this is the first topic I've ever posted on a forum so I appreciate your time for reading this and possibly being some help to me.
 

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if you washed the engine then that is the problem. GM used a poor material to bock out the ks sensor pit in the lower intake manifold. this is a very common code that the sensors are drowned in water and you, have to buy the gm sensors and get the harness.. if you do not need the truck then take it apart and see if its mucked with water corroded connections. then you can buy all the parts .. buy the gasket kit from rock auto felpro gasket about $70..have , to be careful on the model year and engine ..
 

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I never washed the engine, but that doesnt mean the previous owner or dealership didnt. I guess what has me nervous to go through with it all and replace both sensors and harness is that both sensors, through the wire harness, ohm out within specs. That's with me grounding the meter. I wonder if water got in it causing it not to ground correctly. I guess I'll check for an open like between the ecm and the end that plugs into the knock sensor harness. If that passes, then I'll pull the intake and replace both sensors, intake gaskets, sensor harness and use ATV around the rubber plug, and replace the throttle body gasket. Might as well do both sensors, harness, gaskets, and ATV the top sensor plugs and do it all right the first time. My truck does have a slight misfire at idle and I think it's the faulty sensor causing it. Every video I've seen to replace the sensors, they all reuse the intake gaskets which I dont think I'm gonna risk doing. I did notice that when I pop the hood and lift it, that theres a rubber weather strip along the back underside of the hood underneath the wipers that was bent and allowing water in and I wonder if the water was running down behind the engine underneath the intake causing this issue. Someone else said you can cut the wire on the sensor harness on the bad sensor and splice and connect it to the wire going to the good knock sensor. Idk how true that is to temporarily fix my issue til I take the intake off and do some investigating.
 

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as I mentioned this code is a very exact error on the voltage and frequency that the computer has in its memory.. so when just one error is created then it will throw the code. 327 is the front 332 is the rear KS.
yes it can be a PCM connector or the connector harness exterior of the upper manifold . if the pins look good then it is a water problem in this KS area .. GM used a lousy seal that causes many of us to do this work..
if you are a new owner of this then they do power wash it then trouble..
many years ago I used a silicone sealant high temp and blocked up the front of the upper manifold ..
many did use this silicone to seal the KS sensors so the sensor and pins do not get damaged.
the GM manual stated 93K-107K OHMS .
be very careful do not whack the sensors .. if you whack it then it maybe damaged ..
the upper intake manifold most old 5.3L engine do create cracks then the engine will not start good in cold weather reason is the fuel ratio is with too much air .. alcohol on the OEM gaskets got damaged because of the alcohol fuels .. post back how it worked out . some did use aftermarket KS then had to do the job again..
PCM memory will throw code if the aftermarket sensor puts out a different signal..
 
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