Knock Sensor Issues Won't Go Away

[TJay74]

I would do that before I bought the sesors and harness, you are just thorwing money into the issue at this point and running blind.

[jdaniel83]

I took it into a shop that a friend works at the other day and he hooked it up and it was showing voltage at the knock sensors but it was low (can't remember the number). He recommended putting the AC Delco sensors and Delphi harness on it, try some of the Seafoam sprayed through the throttle body treatment, and fill up the tank with some premium to help clean up stuff inside and then bring it back in. Well I did the Seafoam treatment and got the sensors/harness in and installed it all yesterday, and I drove it around all day today (200+ miles) with no SES light or valve clatter. It seems to have its power back and is running much smoother. I'm taking it back into my buddy's shop tomorrow to see what his scanner says but so far I'd have to say it seems that the aftermarket sensors/harness were probably my problem all along. Just goes to show that the first time that I decided not to replace parts with GM or AC Delco products came back to bite me. Lesson learned...hopefully.

[jdaniel83]

Well for those who might be interested I took my truck by my friend's shop yesterday and his scanner showed that everything is working just fine. All knock sensor voltage/ohms showed right where it should and I've put around 350 miles on it since installing the Delco sensors and no SES light or valve clatter. So for anyone that's experienced similar issues to mine don't use aftermarket sensors/harness use either AC Delco or Delphi products. Thanks for the advice everyone.

[Jim01]

I was having the same problem (low voltage input) on my 1997 GMC Sierra k1500, Z71, 5.7L. I replaced the knock sensor 2 times and the wiring once. The problem kept coming back. I recently replaced the M.A.P. (Manifold Air Pressure) sensor and the problem appears to be fixed.

[Disciple78]

I just rebuilt the top end of my 2002 Suburban 5.3 flex and the motor sounds great but after 5 ir 10 miles on the road it throws knock sensors codes on bank 1 and bank 2. I have replaced them 3 times now and followed specs from torque to sealant and same thing runs great until I hit highway speeds and there goes the codes. I am at a total loss myself.

[davester]

It depends on the specific code.  Just because it's a knock sensor code doesn't necessarily mean that it's the knock sensor that's the problem.  If can be a wiring problem, or even a problem somewhere else, that knock sensor happens to notice.  Typically,, for any given code, there is a list of things to go through to find out what the problem is.

[riverbanks]

One possibility is low fuel pressure,lean can cause k.s. codes

[turbo15479]

I moved my knock sensors to the front of the head on the passenger side and by the second spark plug on the driver's side. Running well with no codes for thousands of miles. Why remove the intake it you don't need to? Starting in 2007 GM moved the knock sensors to the sides of the block. Regardless what anyone tells you use AC DELCO sensors as any other ones will throw a code. I have friends who used other brands and they did not work. Amazon sells genuine GM knock sensors for 38.00 each. And if you want your knock sensors on the side of the block Jeg's sells aluminum mount blocks that attach to holes already on the side of the block to relocate the sensors there. They also sell a longer wiring harness that will connect to you connector at the rear of the intake manifold. To check a knock sensor with an ohm meter you should have 93K to 107K on your meter for a good sensor. Then you can put your multi meter on 2 volts and connect one lead to the sensor connector and the other to battery negative. When you tap on a metal part of the engine you should see a small voltage spike which shows the sensor is working. Light blue wire is passenger side and dark blue wire is driver's side. These test are done with engine and key off. The crystals in a knock sensor make their own voltage when vibrated.