NEED HELP CEL with P0332 rear knock sensor - how to test wire?

[trkpony]

Hey all,

I have a 2007 GMC Envoy 4.2L I6. It has about 150k miles on it, I bought it in 2010 with about 35k miles on it, I'm the 2nd owner.

TLDR: P0332 won't go away. I changed sensors and plugs. What's the next step for diagnosis?

Recently replaced all the front end suspension and steering components, and changed the oil.

The vehicle has a leaky valve cover gasket and has had it for a long time, so it has always had a bit of a misfire mostly just noticeable at idle, it hasn't ever effected driving conditions. When I checked in the past, I know there was oil leaking onto the spark plugs.

I got a CEL for code P0332. Which by my search, shows a low input on bank 2 (rear) knock sensor. I turned the key on with engine off, KOEO, and checked the voltage with a meter holding one probe on the negative battery terminal and the other probe on the sensor connector and got a voltage reading of 4.052V. I have read it is supposed to have 5V, so I am not sure if this 4.052V would set off the low input reading for the CEL.

1. Is 4.052V too low for the expected voltage reading on the wiring harness connector?

Since I am getting voltage, and I don't know the answer to the above question, I figured the wiring should be good to the connector, so I went ahead and ordered 2 new AC Delco sensors from RockAuto. I replaced them and torqued them to somewhere around 20ft/lbs (My clicky torque wrench starts at 30ft/lbs and so I used the other manual dial/gauge style torque wrench that I have and tried to get it close/above the 18ft/lbs reading)

Reconnected sensors, reset the CEL with the cheap little reader that I have and drove around. The code came back and is the same, P0332. So then I went and swapped the sensors from the front bank to the rear bank to see if the code would shift from P0332 to a different code for the front bank (P0331?) following a bad sensor after the swap.

I should have tried this swap PRIOR to ordering new knock sensors, but I didn't think about it at the time... anyways, the light still came back on and it is the same P0332. So swapping the sensors didn't shift the code to the front bank, so I assume the sensors are good... I have seen a couple videos on testing the sensors, but I wasn't real confident in my results when I tried to test the sensor by itself. All the videos show a slightly different style sensor, like from the v8 motor and I wasn't sure where to test on the 4.2L sensor.

So THEN, I replaced the spark plugs with new plugs. 41-103 AC Delco plugs. When I pulled the old plugs there were a couple that shows oil all the way down their threads. But I haven't ever received a misfire CEL. Also, the cylinder 3 plug had cracked porcelain. I'm not sure how that would happen?

Pictures of spark plugs attached.

I haven't heard any weird popping or pinging noises that I would think I should hear if I have uncontrolled detonation.

What's the best next step for diagnosis? obviously I need to change out valve cover gasket, but should I run a wire from a pin to the knock sensor connector if the 4.052V isn't good enough? How would I do that?

thanks for reading all this and any help

 

[Mooseman]

The oil on the plugs are likely leaking plug well to valve cover gaskets.

Check the block's ground connections for corrosion or poor contact. Remove and clean thoroughly.

Then, get the schematic of the circuit from the manual from either Charm or Lemon and check for proper continuity, no shorts to ground or voltage. Check the connectors for corrosion at both ends. With both the sensor and PCM unplugged, there should be no voltage or short to ground.

Checking a little further, according to this video, there should be very little voltage to the sensors. Not the same vehicle or engine but his diagnostic process is very thorough.

So I'd compare the voltage between the two sensors. If just the one has voltage, this would need to be investigated further. In that case, I would look for damage in the wiring harness for a short to another wire.

 

[mrrsm]

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Welcome to GMT Nation,

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The First Batch of 20 of 60 Images Follow On:

 

[mrrsm]

Second Batch of 20 Images of 60 Total Images:

 

[mrrsm]

Last 20 Images of 60 Total Images:



End for all Three Posts.

NOTE: Because the Knock Sensor is classified as a "Piezo-Electric" Device that converts the tympanic engine vibrations and untoward shudders from a flexing speaker-cone like set of motions into Electrical Signals that require an Oscilloscope to be able to sense in very fine details and likewise see the images being created during the Tests above to prove that a New KS is working and that other issues (Broken Wiring) are not involved, feel free to drop in on THIS Link and find out whether or not you would like to get an inexpensive one for this problem and not go broke when doing so:

Thread 'How To Use PICO #2204A & HANTEK #1008C Oscilloscopes'

Oct 20, 2019

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(1) Windows or surprisingly... a...

• mrrsm
• Replies: 112
• Forum: Technical Discussion

• 

 

[budwich]

The SM "suggests" a "simple" impedance test of the wiring. Basically, disconnect the sensor. With an ohm meter, measure at the connector, each pin back to a known good ground. The reading should be "OL" (ie. infinity... no continuity)... do the measurement with "key off".

Compare the results for each pin and each sensor. Go from the results.