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L29 454 Knock Sensors

This is a discussion on L29 454 Knock Sensors within the Technical / Maintenance forums, part of the General Discussion category; Anyone mess with the L29 454 Knock Sensors? The reason I ask, is some time back, I checked a KS ...

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    Registered User N0DIH's Avatar
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    L29 454 Knock Sensors


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    Anyone mess with the L29 454 Knock Sensors?
    The reason I ask, is some time back, I checked a KS at Autozone and ohmed it out at 8K. My sensors in my truck ohm out at 8K. My 99 FSM for the 454, says they should be 100K.

    I was going to replace them because the PCM IS giving me a silent KS bank 1 fault. Just don't wanna replace a good sensor with a good sensor..... But the fault is puzzling.

    Anyone know if these sensors go into water jackets? How wet will I get???

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    Can I help you? ksukats57's Avatar
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    Re: L29 454 Knock Sensors

    dunno how wet you will get but have you checked all your wiring, etc? clean connectors on the plug?


    2006 Tahoe Z71

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    Re: L29 454 Knock Sensors

    I checked them last year and they were ok, was able to ohm them ok, at the PCM is where I measured it, so I could "see" both sensors. Then disconnect one and "see" only the other one. Saved trying to ohm out from underneath.

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    Re: L29 454 Knock Sensors

    Quote Originally Posted by N0DIH
    Anyone mess with the L29 454 Knock Sensors?
    The reason I ask, is some time back, I checked a KS at Autozone and ohmed it out at 8K. My sensors in my truck ohm out at 8K. My 99 FSM for the 454, says they should be 100K.

    I was going to replace them because the PCM IS giving me a silent KS bank 1 fault. Just don't wanna replace a good sensor with a good sensor..... But the fault is puzzling.

    Anyone know if these sensors go into water jackets? How wet will I get???
    If you go through the diagnostic chart in the FSM not Haynes or Chilton's and check it all out you will get to the root of the problem, and yes the KS for the big block are different. If you find a bad one replace it with OEM. In the past i have changed them by having the cooling system full and cold leaving the cap on and thus having a vacuum on the system, remove the KS quickly and reinstall new on with little loss of fluid.
    04 K1500 Silverado EXT 3:73 gears, 5.3L 265/75-16,Pace Edwards tonneau,

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    Re: L29 454 Knock Sensors

    Anyone have a 96, 97, or 98 FSM and can look over the Knock Sensor chart and see what resistance it says the sensors are? My 99 shows 100K and with nearly everything pointing to 8K is real, looks like a FSM typo.


    Quote Originally Posted by redvett01
    If you go through the diagnostic chart in the FSM not Haynes or Chilton's and check it all out you will get to the root of the problem, and yes the KS for the big block are different. If you find a bad one replace it with OEM. In the past i have changed them by having the cooling system full and cold leaving the cap on and thus having a vacuum on the system, remove the KS quickly and reinstall new on with little loss of fluid.

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    Re: L29 454 Knock Sensors

    Spec is 8K from ks terminal to engine block, according to GM.
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    Re: L29 454 Knock Sensors

    Thanks, that makes more sense.

    I am curious, maybe with your "connections" at work, can find out. Is the KS Bank 1 fault a real fault with the 454 "J"? Both KS's are in parallel, so they can't really determine left or right without software making the judgement.

    is that a 'normal' fault?

    Now that I am forcing open loop (got a O2 that died on a trip and I disabled closed loop to get it running again), I don't get it anymore. My FSM's are at home, so I can't even look at the troubleshooting chart.

    Thanks!!

    Quote Originally Posted by dietzster
    Spec is 8K from ks terminal to engine block, according to GM.

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    Re: L29 454 Knock Sensors

    On GM's service site there are no bank 1 or bank 2 codes, they only have p0325 knock sensor performance, or p0327 knock sensor circut fault. In either case they want you to check each sensor individualy, so I would say it can not determine specific sides.
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    Re: L29 454 Knock Sensors

    Let me put it back in closed loop and read it again, I didn't copy the code down, just the description.

    Quote Originally Posted by dietzster
    On GM's service site there are no bank 1 or bank 2 codes, they only have p0325 knock sensor performance, or p0327 knock sensor circut fault. In either case they want you to check each sensor individualy, so I would say it can not determine specific sides.

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    Re: L29 454 Knock Sensors

    Confirmed it as the P0325 code. It won't happen in open loop, only in closed. I am forcing open loop right now till I get the O2 replaced that wigged out on me on the trip when it got up to 107F on the trip down to Houston. Wouldn't idle and mpg was 11's on gas, 9.5-10.85 on E85. Went open loop and up to 14's immediately. So that non AC Delco O2 was a real problem. Got the O2 now, just gotta get it in.

    This truck hasn't ever fueled right with those Borg/Warner O2's. Now to do Knock Sensors if I can. Can you send me or post the troubleshooting chart for the KS's for the P0325.

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    Re: L29 454 Knock Sensors

    Looking at my tune, 454 stock calibration doesn't test for P0325 or P0327. So wondering why it is showing up. PM me your email and I can send you my file to look at. Your software might show something mine doesn't (doubt it though)

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    Re: L29 454 Knock Sensors

    IF you are lucky the sensors will have some coolant trash on top of them and the sensor wont leak upon removal.
    For some reason i thought they went into a dead hole on those but my knock sensors arent in a stock location any more. I can look tonite sense the motor is still out.

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    Re: L29 454 Knock Sensors

    --------------------------------------------------------------------------------

    DTC P0325 Knock Sensor Module Performance




    Circuit Description
    The control module contains a removable knock sensor (KS) module which receives the knock sensor input. The knock sensor signal input is filtered by this module before it is input to the controls module. Spark knock is continuously monitored during engine operation. If knock occurs for longer than a calibrated time, this diagnostic trouble code (DTC) will set.

    Conditions for Running the DTC
    • DTC P0327 is not active

    • The engine run time is more than 120 seconds.

    • The system voltage is between 10 and 17.1 volts.

    Conditions for Setting the DTC
    The VCM detects engine knock for more than 50 seconds.

    Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.

    • The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records.

    Conditions for Clearing the MIL or DTC
    • The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed.

    • A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22C (40F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70C (158F) during the same ignition cycle.

    • Use a scan tool in order to clear the DTCs.

    Diagnostic Aids
    Check for the following conditions:

    • A damaged or improperly installed KS module -- Check for the following items:

    - Bent pins

    - Deformed terminals

    - Knock sensor module not completely seated

    • An improperly torqued knock sensor

    Refer to
    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

    in Cautions and Notices.

    Tighten
    Torque the knock sensor to 19 Nm (14 lb ft).

    Review the Fail Records vehicle mileage since the diagnostic test last failed in order to determine how often the conditions occur that caused the DTC to set. This may assist in diagnosing the condition.

    An intermittent may be caused by any of the following conditions:

    • A poor connection

    • Rubbed through wire insulation

    • A broken wire inside the insulation

    Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

    If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.

    Test Description
    The numbers below refer to the step numbers on the diagnostic table.

    This step ensures that the condition is present.

    This step checks for an improperly installed knock sensor module.

    Step
    Action
    Values
    Yes
    No

    1
    Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?
    --
    Go to Step 2
    Go to Powertrain On Board Diagnostic (OBD) System Check

    2
    Important: If you can hear the engine knock, repair the engine mechanical problem before proceeding with this diagnostic.

    Operate the engine within the conditions specified in Conditions for Running the DTC.
    Monitor the Specific DTC info for the DTC P0325 until the test runs with the scan tool.
    Does the scan tool indicate the DTC P0325 Failed This Ignition?
    --
    Go to Step 4
    Go to Step 3

    3
    Turn ON the ignition leaving the engine OFF.
    Review the scan tool Failure Records data for DTC P0325.
    Record the scan tool Failure Records data for DTC P0325.
    Operate the vehicle within the Failure Records conditions.
    Monitor the Specific DTC info for DTC P0325 until the test runs with the scan tool.
    Does the scan tool indicate DTC P0325 test Failed This Ignition?
    --
    Go to Step 4
    Go to Diagnostic Aids

    4
    Inspect the KS signal circuit wiring for incorrect routing near the secondary wires.
    Repair as necessary.
    Did you find a problem?
    --
    Go to Step 9
    Go to Step 5

    5
    Inspect the knock sensor module for incorrect installation.
    Repair as necessary. Refer to Knock Sensor Replacement .
    Did you find a problem?
    --
    Go to Step 9
    Go to Step 6

    6
    Replace the knock sensor module. Refer to Knock Sensor Replacement .

    Is the action complete?
    --
    Go to Step 7
    --

    7
    Using the scan tool, clear the DTCs.
    Start the engine.
    Allow the engine to idle until the engine reaches normal operating temperature.
    Select DTC and the Specific DTC function.
    Enter the DTC number which was set.
    Operate the vehicle, with the Conditions for Setting this DTC, until the scan tool indicates the diagnostic Ran.
    Does the scan tool indicate the diagnostic Passed?
    --
    Go to Step 10
    Go to Step 8

    8
    Important: The replacement VCM must be programmed.

    Replace the VCM. Refer to VCM Replacement/Programming .

    Is the action complete?
    --
    Go to Step 9
    --

    9
    Using the scan tool, clear the DTCs.
    Start the engine.
    Allow the engine to idle until the engine reaches normal operating temperature.
    Select DTC and the Specific DTC function.
    Enter the DTC number which was set.
    Operate the vehicle, with the Conditions for Setting this DTC, until the scan tool indicates the diagnostic Ran.
    Does the scan tool indicate the diagnostic Passed?
    --
    Go to Step 10
    Go to Step 2

    10
    Does the scan tool display any additional undiagnosed DTCs?
    --
    Go to the applicable DTC table
    System OK

  14. #14
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    Re: L29 454 Knock Sensors

    Ok, cool, I will go throught and see what I can come up with.

    I did notice on my datalogger that when I was generally off idle, KR would come up to a fixed amount all the time. I just pulled the pass side wire off, and it doesn't do it now. I'll have to test some more to make sure. That is the easier sensor to work on too. But alas, I have it hot now.... Joy.... Houston heat and a hot BBC.... what a combo. I miss the weather up north.... next week will be back...

  15. #15
    Registered User N0DIH's Avatar
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    Re: L29 454 Knock Sensors

    Hmm...

    Conditions for Running the DTC
    • DTC P0327 is not active (it isn't)

    • The engine run time is more than 120 seconds. (yup)

    • The system voltage is between 10 and 17.1 volts. (yup)

    Conditions for Setting the DTC
    The VCM detects engine knock for more than 50 seconds. (yikes!, gotta be noise or something, can't imagine real knock, none audible for sure, but that is what I see on the datalogger, the KR comes up and stays up)

    Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles. (nope, never see it, PCM is factory told not to show light ever for P0325 or P0327, actually, both are not even checked tests, but yet they apparently are tested)

    • The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records. (doesn't show in FF records, just in DTC's)

    Conditions for Clearing the MIL or DTC
    • The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. (never seen a MIL for it...)

    Well, I think I will mess with it when I get home, drop both sensors and clean the gunk out, 155K probably is a bit gunky down there anyway....

    I have another PCM, with another KM in it, maybe I will just flash it and put it in and see what I get out of it. Would "knock" out the KM and PCM in one shot.
    Last edited by N0DIH; 08-01-2008 at 02:31 PM.

 

 

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