Come along with Eric O. at the SMA shop as he has a look at the infamous GM knock sensors on this 2003 Chevy 1500 with the 4.8. This is a very common problem on many GM trucks and in this video we show you how to diagnose the codes DTC P0327: KNOCK SENSOR CIRCUIT - LOW VOLTAGE - SENSOR 1 & DTC P0332: KNOCK SENSOR CIRCUIT - LOW VOLTAGE - SENSOR 2 using a simple lab scope and some simple testing methods.
The Knock Sensor (KS) system enables the Powertrain Control Module (PCM) to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The system uses 2 KS located under the intake manifold. KS 1 is located at the front of the engine. KS 2 is located at the back of the engine. Each KS produces and AC voltage that varies depending on the vibration level during engine operation. The PCM adjusts the spark timing based on the amplitude and frequency of the KS signal. The PCM used each KS signal to calculated an average voltage range value. If the KS system is operating normally, the PCM should monitor the KS voltage varying above and below the voltage range. If the PCM detects the KS signal voltage within the voltage range, or the KS signal is not present, a DTC will set. DTC P0327 refers to the front KS. DTC P0332 refers to the rear KS.
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50 thoughts on “How to diagnose gm knock sensors – p0327 p0332”
  1. Avataaar/Circle Created with python_avatars Daniel Puig says:

    Good show. Mine shows up as bank 2 which I suspect is the rear but I'll change both.

  2. Avataaar/Circle Created with python_avatars Gene Yus says:

    What a bum, talks like he has marbles in his mouth, lay off the booze!

  3. Avataaar/Circle Created with python_avatars Bishop Bautista says:

    Best walk through and explanation on the net, thank you!

  4. Avataaar/Circle Created with python_avatars Jamie Keaton says:

    They've replaced my knock sensor three times and still getting that code. What else could be wrong? The connector?

  5. Avataaar/Circle Created with python_avatars 3madeamps #3 in nc says:

    iv put 3 new sets and wires .i still have both codes .i got a.c Knock Sensors from a1 auto …

  6. Avataaar/Circle Created with python_avatars Michael Hart says:

    Eric PLEASE HELP ME WITH SOME INFO . I now have a flashing check engine light code p0322 senor 2 circuit low . Going to change both and wire harness . Question is do I have to replace any other gaskets intake , etc .

  7. Avataaar/Circle Created with python_avatars Private says:

    Love this guy!

  8. Avataaar/Circle Created with python_avatars Gregory Craig says:

    Change my knock sensor 4 times still cant get to work cant figure it out

  9. Avataaar/Circle Created with python_avatars Fernando Mendoza says:

    Replaced the engine on a 2005 Tahoe. The incoming engine had its own knock sensors. After install I had code for low voltage knock sensor 1. Replaced both sensors and harness. It now says low voltage knock sensor 2…….
    Did resistance and continuity checks on both sensors and harness. All ok. Decided to replace sensor two with different brand just in case but same result. Low voltage sensor 2. Swapped sensor 1 with sensor two. Problem remains. Low voltage sensor 2. Any suggestions???

  10. Avataaar/Circle Created with python_avatars old biker says:

    keep washing your engine bay with a water hose or car wash wand ,and this will be the end result .

  11. Avataaar/Circle Created with python_avatars ChineeyMark_BxNY says:

    What's the torque spec for a gmc yukon 5.3L?

  12. Avataaar/Circle Created with python_avatars Chris Thorndike says:

    Hey Eric, thank you for posting the video as always!! I know this was posted a while ago. But I was wondering if the knock sensor itself can actually cause the engine not to start. It’s the only code that’s popping up on the ole 05 6.0 gmc. Any information would be a great help. Thank you very much!

  13. Avataaar/Circle Created with python_avatars Robert Shields says:

    What is the resistance fluctuates or is higher that spec's?

  14. Avataaar/Circle Created with python_avatars jcbenson01 says:

    Thank you SOOO much. Very thoroughly and simply explained. Admittedly, I’m not very good with my scope. But I’m getting it powered up and Gonna play around with her. I’m getting low voltage codes on both. I suspect I have a problem between the main harness and pcm

  15. Avataaar/Circle Created with python_avatars Carlos Dxsman says:

    Thanks for your time and taking the video, you are very professional

  16. Avataaar/Circle Created with python_avatars Lance Ladue says:

    Thanks for the incite ..I have a 06 Chevy…I do appreciate your way of explaining..and if you were making this video in 2020 your cold would probably be labeled as covid…thanks again…

  17. Avataaar/Circle Created with python_avatars Jose Nazario says:

    Hi Eric, question; I have a 2007 GMC Sierra with a vortex max 6.0. Has 175000 miles and it runs great, but I recently got me a P0333 code. It’s come and goes about 2 times. Now is off and is being like a week with the code off. What do you think is going on?

  18. Avataaar/Circle Created with python_avatars David James says:

    so….. a knock sensor is just a microphone. same characteristics

  19. Avataaar/Circle Created with python_avatars Brandon P says:

    Just with a volt meter on AC I got .4v on one smacking with hammer and .05 on the other. Thanks! Can't afford a scope

  20. Avataaar/Circle Created with python_avatars LittleOldBoat says:

    Thanks for posting

  21. Avataaar/Circle Created with python_avatars Juan Rios says:

    good job man

  22. Avataaar/Circle Created with python_avatars Philly Dee says:

    Cool diag and fix😎

  23. Avataaar/Circle Created with python_avatars robert Last says:

    dude i really like your viedios you explain stuff very well thanks

  24. Avataaar/Circle Created with python_avatars jolee51282 says:

    Hey I have the same problem with my silverado, the knock sensors. How's are they now. Do you have a link for the sensor and harness

  25. Avataaar/Circle Created with python_avatars rasz mataz says:

    02 avalanche had same problem new knock sensors and harness still have same code after replacement cleared code still keeps coming back,any idea?

  26. Avataaar/Circle Created with python_avatars Robert Candelaria says:

    I'll subscribe when I see an answer to the "multiple questions" about replacing the KSs and the the alarm codes coming back in shortly after, as the same happened to me. I've reset the alarm twice by disconnecting the battery but the alarm comes back in. Resistance tested good on the new KSs but I don't have and can't I afford a scope.

  27. Avataaar/Circle Created with python_avatars O P says:

    Can you test the knock sensor circuit from the pcm?

  28. Avataaar/Circle Created with python_avatars scott McIntosh says:

    15 inch pounds

  29. Avataaar/Circle Created with python_avatars Michael Luecke says:

    Replaced both mine with wiring harness and now my engine light comes back on for bank 2 knock sensor could i have bought a faulty knock sensor

  30. Avataaar/Circle Created with python_avatars Angel C says:

    What if I put in new sensors and harness and drove it around and the engine light still didn’t turn off? And now it’s idle is rough?

  31. Avataaar/Circle Created with python_avatars Dave May says:

    Any reason why I could replace it all by the book & get the same code, again?

  32. Avataaar/Circle Created with python_avatars InsideOfMyOwnMind says:

    Your tap test sounds just like an old ford I had when idling…..til I sold it lol.

  33. Avataaar/Circle Created with python_avatars G Sams says:

    Bahahahah hows your 14 yr old Honda running… oh that's right it isnt… Love ya man…

  34. Avataaar/Circle Created with python_avatars # says:

    Will the car run just fine with one good knock sensor. My ford has a code on bank 2 – P0330 but car feels and sounds fine. Can I still drive while I wait for a new sensor?

  35. Avataaar/Circle Created with python_avatars Adolfo Salazar says:

    Bro go easy with the yayo it's a business rule you should now that in fact its business rule #2 (dont get high on your own supply) but of course not everyone follows the rules right

  36. Avataaar/Circle Created with python_avatars Scott Hodges says:

    Thanks for the great video…. especially the use of a multi meter….still working on getting a modis…verus out of my range…i work on family and friends as time allows…you know, for free labor

  37. Avataaar/Circle Created with python_avatars Noah Video channel says:

    Been chasing this problem on my Firebird, always circuit one low volts. Thought I had replaced both sensors and the harness, code came back almost immediately, its been on and off since then. This is great information, I'll start looking at this more, maybe I bought a bad sensor.

  38. Avataaar/Circle Created with python_avatars Peter Parker says:

    Thanks man. Really helpful videos.

  39. Avataaar/Circle Created with python_avatars Mike Duane says:

    Just had this occur on my 2004 GMC Sierra pickup. Had to order the parts where ever I was getting them from, so I decided to check around various places to source the parts. Funny how the price changes depending on where you get it from. The Chevy dealership wanted $99 each. The local AutoZone parts store could get them in a day for $72 each. Then I just happened to take a chance and ran the part number through the WalMart website and lo and behold…..$35 each, shipped to the local store for free in two days. All prices were for AC Delco OEM parts. WalMart even showed the wiring harness from the sensors to the connector on the top of the engine was available for $42. Gotta love competition.

  40. Avataaar/Circle Created with python_avatars Captain0Beaky says:

    Thank you for that video. I've got a Knock Sensor fail on a GM Astra, and seeing you check the input has given me the energy to finally get my PC-Based scope installed on my laptop and prove the fault.

    I'm starting out as a full time workshop since April, so my kit is not as advanced as yours (although electronics is my passion, and Im already a "very very very advanced" DIY'er), but I did get around to setting up my Hantek computer scope, and diagnosed an identical problem with a 2003 Opel Astra.

    My background is in Aerospace system design for Rolls-Royce, but I have had to leave full time work due to illness so I've ended up setting up a small engineering shop in Madeira, Portugal (almost by accident|!)

    My approach to diagnostics is similar to yours – "Prove the root cause then change the right part" – this approach is serving me well – I'm already inundated with work – I get all the weird problems – the stuff other garages hand off (weird diagnostics problems etc) , or won't take on ( complex oddities like Rolls-Royces and Land Rovers ). My favourite is cars that have had the "Parts Shotgun" and still aren't fixed!. It's really keeping me entertained!

    Funny thing happened the other day – a guy arrived at the workshop with his new purchase – a very nice clean '02 Land Rover Discovery 2 V8.
    These are very rare here – in fact, this is the only other V8 Land rover I know on the island! (Mine is the other one!)
    He was very proud, and asked me to have a look at his new purchase (This is common, many garages (myself included) will give an "assessment" for free – usually the customer goes to the cheapest, and end up getting raped by a garage that doesn't fully understand the work)
    Like you, I tell it like it is, and if they go elsewhere, then that's fine by me – I pride myself by being honest and fair, even if the customer isn't.
    I immediately recognised that it was missing on at least 2 cylinders, and popped the bonnet to check it out.
    Found 2 ignition leads adrift and not on the spark plug, and one completely failed! I plugged them back in and temporarily patched the third so it's running on 8 cylinders now.
    I complimented him on finding such a clean example, and we had a chat about the car (I have an identical diesel variant of the same car also)

    The customer went from "can you have a quick look at it and give me a quote" to " When can you take it in and sort it all out for me?"…..
    I'm taking the car in when he goes back to the mainland in 2 weeks!!! RESULT – I will have a decent amount of time to work on the car and wait for parts.

    Keep up the good work – I enjoy your honest and realistic diagnostics and also picking up tips – I've just bought a "big nasty" of my own!!
    And I'm looking into the various diagnostics options available here.

    I'm sorted for a few manufacturers (VW Group, Land Rover, Mercedes) but as I do more diagnostics work, I could do with the easy access to circuit diagrams etc…

    Loving the Youtube channel – If you fancy a trip to Madeira (Portugal), let me know – If you like classic cars – aim for the last weekend in May!


    P.S. Extra credit for saying "Aluminium" and not "Aluminum"!!!

    P.P.S = extra credit and my regards to Mrs "O"

  41. Avataaar/Circle Created with python_avatars Carlyle Roberts says:

    Very helpful video, thanks!

  42. Avataaar/Circle Created with python_avatars Dels Transs says:

    Great vid Question will these codes cause loss of power and gas mileage>

  43. Avataaar/Circle Created with python_avatars Mike Chiodetti says:

    Great Video! Hope the cold died quickly! Thanks to Miss Hannah for her help. How's she doing? Coming back to S.M.A. anytime in the near future? No cold in the last five years? Must have been all the brakkleen snorting!

  44. Avataaar/Circle Created with python_avatars Daniel McCabe says:

    Can these being bad throw a random misfire code also?

  45. Avataaar/Circle Created with python_avatars Duncan Mac says:

    Thanks for the video.