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I own a 2000 Silverado Z71 3dr ext cab 5.3L and my SES light came on. i checked and i am getting back code PO327 and PO332 (knock sensor circuit, low output). what is the easiest way to determine if the actual knock sensors need to be replaced or if its the knock sensor harness connector?
 

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Thank you for the help. Anyone know how hard it is to get to the knock sensors and what tools are required. I'm pretty sure they are under the intake manifold, which doesn't sound like fun.
 

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They are under there, but can't help you with tools. Sorry, Never done one on a 5.3L
 

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There is a bullentin on that from GM (where I work) "0332" is a ground fault in the knock sensor wiring set off by moisture (there are two, but it won't tell you which one). Easy to get at - just remove the intake manifold, the sensors sit in a metal valley pan. Don't remove the pan, just the boots over the sensors and the sensors themselves. Put in new sensors, silicone between sensor and boot and wire and boot. Replace intake manifold, with new gaskets - your in there anyways... And your code should stay cleared.
 

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And yes, you will need a tool to disconnect the fuel supply line from the fuel rail. But, other than that - nothing but an average tool kit. Ask your local GM/Chevy dealer for a few pictures of the intake manifold and knock sensor locations. Any nice parts guy will do it for you, maybe with a coffee or dounut... we parts guys work for these all the time
 

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Some info that might help:
From: Allexperts
Answer
Hi
Why are they suggesting the replacement of a Knock sensor?
Is the Check Engine light on?
If the check engine light is NOT on, there is NO reason I can think of to replace the sensor.
If it is on, I know the GenII engines (1999-2002) had a problem with water getting into the knock sensor mounting holes, and creating codes due to short circuits (Code P0332) for the REAR sensor ONLY. If you have a code P0327
that is for the front sensor ONLY. No need to replace them both. If you happen to have a code P0325, this code means that someone, somewhwers replaced the PCM (computer) and did not swap the Knoch Sensor Module into the new PCM computer.
Testing...Remove the intake manifold sight shield.
Disconnect the knock sensor jumper harness connector located on the left side of the intake manifold.
Set the DMM to the 400K ohm scale.
Measure the resistance of the appropriate knock sensor using the DMM connected to battery ground.
Is the resistance of the knock sensor between 93 and 107k ohms.
If so the sensors are good
If not Connect the DMM between the appropriate knock sensor signal circuit on the sensor side and the engine block.
Set the DMM to the AC voltage scale.
Important: Do not tap on plastic engine components.
Tap on the engine block near the appropriate knock sensor while observing the signal indicated on the DMM.
Is any signal indicated on the DMM while tapping on the engine block near the knock sensor?
If so check all wires to PCM.
If not replace sensor(s) for the code set.
I hope this helps.
JUST advice from experience.
Good Luck
Pawl
 

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Hi, let me just add, I just replaced my knock sensor#2 two months ago, with silicone, and got an alarm again. It, and #1 had 100k-ohms, and 0.2V AC when knocked with hammer on block's side (suppose to be 5V, but digital meters never show spikes). I took off the upper manifold again, and found the #2 sensor was rusted again. I asume water is running down the wire, so $50 later (because I did not want to trust a rusted sensor even though it checked out) I replaced it and siliconed everything. A few things I learned: don't use anti-seize (the voltage is weak already), tighten to 10-15ft/lb, and double check that the well is clean of all rust and water (it is hard to see, unless you jump on your engine). Good Luck.
 

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It's been a while since anything was posted here, but I just went through the knock sensor fiasco and learned a lesson the hard way on my 2001 Suburban (225,000 miles). I purchased cheap sensors online for less than $20 for the pair. Installed them and had a SES light a couple days later. After much debate, I purchased a pair of OEM sensors for over $100. Before I put them in, I checked the $10 sensors with an oscilloscope (1st trace below). The voltage setting was on 200 mV/division, so the signal shown is about 1 V peak-to-peak. I then removed the sensor and replaced them with the OEM parts torqued to the same value. I then did the same test with the oscilloscope (2nd trace below). This time, however, the voltage setting is 2 V/division, so the signal is about 14 V peak-to-peak, more than 10 times higher than the cheap sensors. Both cheap sensors has about the same sensitivity (as did both OEM sensors), so this is very unlikely to be just two defective cheap sensors. They just do not have the performance of the OEM sensors. I am all for saving money when reasonable, but if you have to replace knock sensors, do yourself a favor and spring for OEM sensors.
 

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It's been a while since anything was posted here, but I just went through the knock sensor fiasco and learned a lesson the hard way on my 2001 Suburban (225,000 miles). I purchased cheap sensors online for less than $20 for the pair. Installed them and had a SES light a couple days later. After much debate, I purchased a pair of OEM sensors for over $100. Before I put them in, I checked the $10 sensors with an oscilloscope (1st trace below). The voltage setting was on 200 mV/division, so the signal shown is about 1 V peak-to-peak. I then removed the sensor and replaced them with the OEM parts torqued to the same value. I then did the same test with the oscilloscope (2nd trace below). This time, however, the voltage setting is 2 V/division, so the signal is about 14 V peak-to-peak, more than 10 times higher than the cheap sensors. Both cheap sensors has about the same sensitivity (as did both OEM sensors), so this is very unlikely to be just two defective cheap sensors. They just do not have the performance of the OEM sensors. I am all for saving money when reasonable, but if you have to replace knock sensors, do yourself a favor and spring for OEM sensors.

well your post of these measurements , I would like to know what "your" codes were with the cheap sensors ?
also as you know the sensor output is dependent on engine noise. I would have liked to see a trace with more pulses not just the one pulse.
with all the pulses it gives a better understanding of the sensor ability to produce the signal based on engine noise.

O2 and the ks should be OEM because these will cause the PCM to throw codes and effect engine performance with other manufactures products. output will vary.
These KS fail because water enters in the front of the engine .The space opening between the upper and lower manifold GM used a sponge type material not water proof and over time disappears. the use of a sealer is used to close this opening also leave the rear open so any moisture that does get in can vent out.
 

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this is a good video of KS troubleshooting. scope indications of the KS and the timing being retarded . also the reading of the 5 volt bias voltage.

engine being tested has worn engine parts so this is a good indicator of the KS responding to the engine noise.

on engine like this being tested some may use teflon tape on the KS threads that will mess up the KS bias volts. sensor needs a good ground.
 

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I had a brief dialogue with JCat before doing my KS repair, (easy repair is a relative term, since never having done it, but i had zero problems and code never returned)

You MUST follow all the innovation behind remediating this problem for the life of the vehicle this includes: RTV dam around the upper knock sensor in a U shape. Removal of the sponge crap material (surprised nobody makes a replacement part that fits and is water proof) and then a horizontal dam made of silicone to prevent entry of water at the front of the intake manifold. (rear of manifold is of course left open so it can drain any moisture that does enter the valley)

That is how i did it, with Delco Knock Sensors from AC Direct on amazon, Delco Gaskets, and Doorman Knock Sensor hanress (0ld harness was still good, OEM was not available for purchase)

The total of the parts alone cost me $175 and that was thru online retailers, not "cheap" in my terms at least. however, the real savings is when you tear into it yourself.

One thing I can say is, DO NOT EXPECT TO BE FINISHING THIS IN 2 HOURS. Dedicate at least 4-5 Hours for this. For the cleaning of the valley detailed below.

Reason being is that your intake valley is probably VERY DIRTY and will need to be sucked out with a wet/dry vac. I did EXTENSIVE CLEANING to the entire intake valley area. And had I beaucou money I would have simply replaced the entire intake valley as well. I spent alot of time cleaning it. Trust me, those of you taking it to a shop to get this fixed, they will NOT BE SCRUBBING YOUR VALLEY CLEAN FOR A PROPER RELIABLE, LONG LASTING FIX.
 

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well your post of these measurements , I would like to know what "your" codes were with the cheap sensors ?
also as you know the sensor output is dependent on engine noise. I would have liked to see a trace with more pulses not just the one pulse.
with all the pulses it gives a better understanding of the sensor ability to produce the signal based on engine noise.

O2 and the ks should be OEM because these will cause the PCM to throw codes and effect engine performance with other manufactures products. output will vary.
These KS fail because water enters in the front of the engine .The space opening between the upper and lower manifold GM used a sponge type material not water proof and over time disappears. the use of a sealer is used to close this opening also leave the rear open so any moisture that does get in can vent out.
I had both bank knock sensor codes (P0327 and P0332) within a day or so of installing the new cheap sensors. This was because their output was insufficient to keep the computer happy. I did measurements with the intake off so I could make a direct comparison between the new cheap sensors and the new OEM sensors under very similar conditions (same torque, tapping on the engine about the same, same temperature, etc.), thus I did not post any engine running traces. Note that the traces are open circuit measurements, going into the 1 Mohm input impedance of the scope through a 10X probe with the engine computer disconnected.
 
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