Yes, I had the dreaded knock sensor code for the rear sensor pop up after washing my engine.

I spent $200 + on TWO new sensors, the wiring harness brand new from GM and a set of fel-pro intake gaskets.

Not only was the problem not fixed, but now the FRONT one os coding also...

I'm guessing that I'll be tearing back into everything again, but I want to know if any of you others have had this happen and if there is anything I can do before i go back in.

BTW, I did have the original code cleared immidiatly after finnishing the work the first time, less that 100 miles later it threw the codes for BOTH sensors. Cleared it once more and yet again on my way to work this morning they came around once again.

 

The first three things that come to my mind are a pinched/shorted wire in the knock sensor harness, plugs not seated all the way onto the sensors, or that the knock sensor harness is not correctly plugged into the engine wiring harness.

 

I would say that there is a connection problem with the wiring harness. What did you tq the new knock sensors to?.....they can be over tightened and give incorrect readings.....also they can be dropped and knocked out of spec. They are pretty sensitive. Also did you make a water dam with RTV to prevent the cavities being filled with water from future washings? I know there is a TSB out about the RTV dam.

 

Well ****. I finger tightened them and then snugged them with a ratchet.

Is there a specific torque spec for them? And chance you might know what it is?

I didnt build a "dam", I went ahead and put silicon around the caps themselves and popped them in.

Looks like a teardown and re-work....

 

I think I had a rear code that just wouldn't turn off no matter what, so I deleted it in the tune...lol

 

Start with the easy part first...make sure the sensor harness is connected correctly to the engine harness. You can also take a multimeter and check the resistance of both without pulling the manifold. Put one probe on each pin of the harness connector, and put the other probe to some exposed aluminum up top, like the top engine cover. IIRC they should both be around 10K ohms.

 

just to make 1 bajillion percent sure....

Did you mean 10K (Ten thousand) Ohms? OR 100K (One-Hundred Thousand) Ohms??

Mine are reading 100K Ohms reading the pin on the KS harness side and grounded to the alternator aluminum casing....

 

The procedure I found shows to look for resistance to be between 93k and 107k ohms. Also, you can set your DMM to AC voltage and tap on the block to make sure there is a signal generated.

 

Ok, so somehow i managed to delete a large part of my text in post #7...

I had 5 Ohms originally because i managed to pinch the harness. A stupid mistake of course.

After Complete disassembly, i inspected the wires and found no breaks in any of the wire strands so i just taped them good and crossed my fingers i won't have to tear into it again and replace the new harness with another new harness...

 

Sorry, should have been 100K.

Hopefully you got it figured out!