Results 1 to 11 of 11

Thread: Knock Sensor normal voltage and operation

  1. #1
    Supporting Member Turbo Mopar Contributor turbo84voyager's Avatar
    Join Date
    Jul 2008
    Location
    Nanticoke PA
    Posts
    805

    Knock Sensor normal voltage and operation

    I moved my knock sensor on my 2.4 to the stock 2.4 location (2.5 Sensor) but I had to make an adapter ( A bolt with a nut welded to the head) since the thread in the block is M8 and the sensor is 3/8. I have a newer block and the early 2.4 sensor is M10. Anyway driving around I normally see 0 volts with a an occasional 0.1 - 0.2 volts. I did see a 0.5 at one point but that was about it. If I rev the engine I really don't see any voltage other than 0.1 or 0.2 and most of the time it is 0. My question is on normal operation do these always generate some voltage and my sensor is weak or is this normal operation. I am using a snap-on 2500 red brick to monitor the sensor. I was getting similar readings when it was mounted to the intake. I would have expected a small amount of voltage just about all the time with a slight increase as the RPM's go up. This is an aftermarket replacement sensor I had on my 2.5 for a few years. Thanks, Justin
    Justin
    84 Plymouth Voyager LE 2.5 Intercooled Turbo 5-spd - Only 84 Turbo Van!
    89 Dodge Caravan ES 2.4 SRT-4 Intercooled Turbo (46 trim, OS Valves, CP Pistons, Eagle Rods, NPR IC) Built 31th trans
    91 Dodge Shadow Convertible 2.5 Intercooled Turbo A555 5-spd
    01 Pontiac Grand Prix GTP - 3.8 supercharged! Only 5K miles....
    01 Subaru Forester - Daily Driver
    07 Yamaha FJR 1300 140+ HP on 2 wheels
    85 Honda Nighthawk 450
    94 Bobcat 763 Skidloader 2.2 Kubota Diesel
    SV-SDAC Member

  2. #2
    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
    Join Date
    Feb 2006
    Location
    Mesa, AZ
    Posts
    2,427

    Re: Knock Sensor normal voltage and operation

    You are going to get more "noise" with more RPM. If you look at a stock knock scale it take more voltage to be considered "knock."

  3. #3
    Supporting Member Turbo Mopar Contributor turbo84voyager's Avatar
    Join Date
    Jul 2008
    Location
    Nanticoke PA
    Posts
    805

    Re: Knock Sensor normal voltage and operation

    That's what I expected to see but for the most part the scanner shows 0v with the occasional 0.1-0.3. I'm thinking its a bad sensor. I moved it to the block and there was very little difference from the intake.
    Justin
    84 Plymouth Voyager LE 2.5 Intercooled Turbo 5-spd - Only 84 Turbo Van!
    89 Dodge Caravan ES 2.4 SRT-4 Intercooled Turbo (46 trim, OS Valves, CP Pistons, Eagle Rods, NPR IC) Built 31th trans
    91 Dodge Shadow Convertible 2.5 Intercooled Turbo A555 5-spd
    01 Pontiac Grand Prix GTP - 3.8 supercharged! Only 5K miles....
    01 Subaru Forester - Daily Driver
    07 Yamaha FJR 1300 140+ HP on 2 wheels
    85 Honda Nighthawk 450
    94 Bobcat 763 Skidloader 2.2 Kubota Diesel
    SV-SDAC Member

  4. #4
    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
    Join Date
    Feb 2006
    Location
    Mesa, AZ
    Posts
    2,427

    Re: Knock Sensor normal voltage and operation

    Try tapping the area around it with a 3/8" drive extension while watching the scan tool. Sometimes you have to hit it just right to see any movement.

  5. #5
    Supporting Member Turbo Mopar Contributor turbo84voyager's Avatar
    Join Date
    Jul 2008
    Location
    Nanticoke PA
    Posts
    805

    Re: Knock Sensor normal voltage and operation

    that's the funny thing. I did this and like you said I had to do it just right and multiple times fast enough sure enough I saw a brief 3 volts. That's why I thought it was working, but while on the engine it barely does anything. I'm stumped. I have another one I can try and see what happens.
    Justin
    84 Plymouth Voyager LE 2.5 Intercooled Turbo 5-spd - Only 84 Turbo Van!
    89 Dodge Caravan ES 2.4 SRT-4 Intercooled Turbo (46 trim, OS Valves, CP Pistons, Eagle Rods, NPR IC) Built 31th trans
    91 Dodge Shadow Convertible 2.5 Intercooled Turbo A555 5-spd
    01 Pontiac Grand Prix GTP - 3.8 supercharged! Only 5K miles....
    01 Subaru Forester - Daily Driver
    07 Yamaha FJR 1300 140+ HP on 2 wheels
    85 Honda Nighthawk 450
    94 Bobcat 763 Skidloader 2.2 Kubota Diesel
    SV-SDAC Member

  6. #6
    Supporting Member Turbo Mopar Contributor turbo84voyager's Avatar
    Join Date
    Jul 2008
    Location
    Nanticoke PA
    Posts
    805

    Re: Knock Sensor normal voltage and operation

    I was hitting the sensor pretty hard to get the 3 volts.
    Justin
    84 Plymouth Voyager LE 2.5 Intercooled Turbo 5-spd - Only 84 Turbo Van!
    89 Dodge Caravan ES 2.4 SRT-4 Intercooled Turbo (46 trim, OS Valves, CP Pistons, Eagle Rods, NPR IC) Built 31th trans
    91 Dodge Shadow Convertible 2.5 Intercooled Turbo A555 5-spd
    01 Pontiac Grand Prix GTP - 3.8 supercharged! Only 5K miles....
    01 Subaru Forester - Daily Driver
    07 Yamaha FJR 1300 140+ HP on 2 wheels
    85 Honda Nighthawk 450
    94 Bobcat 763 Skidloader 2.2 Kubota Diesel
    SV-SDAC Member

  7. #7
    Supporting Member Turbo Mopar Contributor turbo84voyager's Avatar
    Join Date
    Jul 2008
    Location
    Nanticoke PA
    Posts
    805

    Re: Knock Sensor normal voltage and operation

    I swapped the sensor with another used sensor I had and I am still only getting very small amount of voltage appearing on the scan tool. I scaled the knock voltage tables down and drove the van. I did get the CEL on knock to light and the scan tool was reading 0 or a very low voltage that I wouldn't expect the light. Is it possible the MT2500 ( red brick) is too slow to monitor knock. But then again during normal driving the voltage was at 0 most of the time. Im thinking about getting another knock sensor and give it a try
    Justin
    84 Plymouth Voyager LE 2.5 Intercooled Turbo 5-spd - Only 84 Turbo Van!
    89 Dodge Caravan ES 2.4 SRT-4 Intercooled Turbo (46 trim, OS Valves, CP Pistons, Eagle Rods, NPR IC) Built 31th trans
    91 Dodge Shadow Convertible 2.5 Intercooled Turbo A555 5-spd
    01 Pontiac Grand Prix GTP - 3.8 supercharged! Only 5K miles....
    01 Subaru Forester - Daily Driver
    07 Yamaha FJR 1300 140+ HP on 2 wheels
    85 Honda Nighthawk 450
    94 Bobcat 763 Skidloader 2.2 Kubota Diesel
    SV-SDAC Member

  8. #8
    Supporting Member II Turbo Mopar Contributor A.J.'s Avatar
    Join Date
    Feb 2006
    Location
    Mesa, AZ
    Posts
    2,427

    Re: Knock Sensor normal voltage and operation

    Maybe you're not getting any knock? That's a good thing.

  9. #9
    Moderator Turbo Mopar Staff Vigo's Avatar
    Join Date
    Feb 2006
    Location
    San Antonio,TX
    Posts
    10,798

    Re: Knock Sensor normal voltage and operation

    I wish i had an answer for this. Sucks that the stock sensor signal is not easy to interpret even for smart people.

    Dont push the red button.You hear me?

  10. #10
    turbo addict
    Join Date
    Dec 2011
    Location
    Hemet,CA
    Posts
    1,636

    Re: Knock Sensor normal voltage and operation

    exactly how is the scanner observing the knock sensor voltage?

    I wouldnt expect any sort of human interpretable direct voltage reading coming from the knock sensor. Its just a piezo microphone. Reading a voltage from it with an AC or DC voltmeter would almost certainly tell you nothing as the response rate from those instruments is far too slow and the sonic events that you are trying to observe are very short and fast. Perhaps with an oscilloscope you could start interpreting the data.

    Now if the scanner is outputting the filtered and processed "voltage" that the ECU is internally using to determine knock, thats another story.

  11. #11
    Supporting Member Turbo Mopar Contributor turbo84voyager's Avatar
    Join Date
    Jul 2008
    Location
    Nanticoke PA
    Posts
    805

    Re: Knock Sensor normal voltage and operation

    AJ, I hope your right. I am running very conservative timing especially in boost. I don't hear any knock and I was driving around my house ( country roads) with no hood so I really think I would have heard something if it was bad enough. As for the scanner, I never monitored knock with it on any other vehicles before so I don't know how well it works. In the data section it shows knock sensor voltage and it shows how much timing is being pulled at each cylinder. I believe this sensor is more active than the last but I ordered a new one this evening so ill give that one a try. One thing im not sure how much it effects the sensor reading is the engine rotating assembly was balanced, and even though it has forged pistons they are extremely quiet. This engine is far smoother than any 2.2 or 2.5 I have ever had and it doesn't have balance shafts. Sorry for any confusion here, I just want to try to get the knock control working as best as possible. That is the main reason I didn't go with an aftermarket ecu. Thanks Justin
    Justin
    84 Plymouth Voyager LE 2.5 Intercooled Turbo 5-spd - Only 84 Turbo Van!
    89 Dodge Caravan ES 2.4 SRT-4 Intercooled Turbo (46 trim, OS Valves, CP Pistons, Eagle Rods, NPR IC) Built 31th trans
    91 Dodge Shadow Convertible 2.5 Intercooled Turbo A555 5-spd
    01 Pontiac Grand Prix GTP - 3.8 supercharged! Only 5K miles....
    01 Subaru Forester - Daily Driver
    07 Yamaha FJR 1300 140+ HP on 2 wheels
    85 Honda Nighthawk 450
    94 Bobcat 763 Skidloader 2.2 Kubota Diesel
    SV-SDAC Member

Similar Threads

  1. Electronics T3 knock sensor and knock sensor harness
    By 168glhs1986 in forum Parts Wanted
    Replies: 2
    Last Post: 03-29-2014, 05:49 PM
  2. Replies: 22
    Last Post: 06-26-2013, 07:11 PM
  3. Knock voltage readings and thresholds
    By Force Fed Mopar in forum EFI Tuning
    Replies: 23
    Last Post: 09-03-2012, 01:08 PM
  4. Replies: 3
    Last Post: 05-05-2012, 09:12 AM
  5. Knock voltage less than 0.8 volts
    By TopDollar69 in forum EFI Tuning
    Replies: 9
    Last Post: 08-19-2008, 08:08 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •