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2001 GMC Yukon - Knock sensor

So my service engine soon light was on it was a bad knock sensor low voltage code but then it suddenly went off again the light is still good so what’s the issue?

What exactly are you saying? Did you have the original problem fixed and the code has reappeared? Did you just wait until the light went off and now it’s on again? Did you have the problem fixed and now the light is on again for a different code?

No the code just went away I have been waiting on my next paycheck to fix it the light went off on its own with no repairs and I know the light works it still lights up on ignition

If the condition causing the code stops, then the light will turn off after a certain number of drive cycles. I’d leave things alone for now if I were you

So you thing the magic engine knomes fixed it or I just had something loose?

Could be either/or! But seriously, if it’s something that is loose, the light will probably come back on fairly soon, and then you can try to change the sensor at that time.

Ok I know it’s not a cheap fix because it’s inside my intake manifold the cheapest ASE certified place is Blumenthal here in OKC for the knock sensor wire harness and sensor as well as new valve seals was $811

A wild donkey guess from your cryptic description is that there may be 1) a failing sensor or 2) damaged wire to that sensor

Have you done any other work to this truck recently? I washed my engine bay (2000 GMC) and almost immediately after, I got a code for Knock Sensor low voltage. After a couple of drives, the code went away. I figure the wires are getting a bit old, and getting them wet caused an error code, and now that they are dry- no more issues.

We have a lot of Yukons with the 5.3 liter V8 in our fleet

And here’s what you will need for a proper repair

2 knock sensors

knock sensor sub harness

the valley pan gasket

intake manifold gaskets

the knock sensor gaskets

The knock sensor gaskets get hard as a rock, causing the knock sensors and the harness to get severely corroded.

You do everything at the same time

no ifs ands or buts

The good news is that this isn’t an especially complicated repair. Any competent shop . . . how you would determine if that’s the case is another story . . . should be able to do this. No special tools are needed

But there really are no shortcuts

the knock sensor gaskets are the root cause. No point in removing the intake, only to do a half ___ repair, in my opinion

There’s more good news . . . since you’ll be replacing the intake gaskets, the truck might actually run better, especially when cold. After all, those intake gaskets are probably hard as a rock by now, if they’re still original. And flat intake gaskets can contribute to all sorts of other problems