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Knock sensor

07-21-2007, 03:12 PM
Hey guys.can anyone tell me where the knock sensors are located on an 01 4.8? I've heard under the intake manifold but that sounds kinda wierd. Apparently my truck is showing the trouble code po332 which is the bank 2 knock sensor. it seems like this is actually a common problem because they tend to leak around where the sensor goes in, and i have cleaned my engine more than seems possible that i messed it up, but i dont actually see the thing. thanks

07-22-2007, 04:11 PM
Yup that's what the Haynes Manual Says. Remove Intake manifold and they are directly beneath that. Why o Why, Why o Why, Why o Why, did GM put those F*ck'in things there. Seems pretty ridiculous to me anyways.

Let us know how you make out?

07-23-2007, 02:11 PM
so in order to even check to see if the connection to them is bad i have to remove the manifold and thus replace the gasket to that? nice

07-23-2007, 07:58 PM
You can see it if you look up at it from under your truck. It is a bitch to even see, so I doubt you would have room to swing a wrech, but it might be worth a try.

07-23-2007, 07:58 PM
If they're like the '03's, the gaskets are plastic with an embedded silicone (I think) seal that you can reuse.

07-24-2007, 01:43 PM
yeah i thought about that after the fact haha.i got the intake off anyway.but which one is bank 2? i wanna assume its the back one, and thats the one that looks in bad shape

07-24-2007, 01:46 PM
I would replace them both while you're under there. Not positive which is which...

07-24-2007, 01:49 PM
yeah i probably.thanks for the help

07-25-2007, 06:29 AM
Some guys will squirt some silicone around the rubber seal of the knock sensors to keep water out. The water tends to get in at the front of the intake manifold where the foam piece is. Small piece of prevention to prevent them from corroding again.

07-25-2007, 02:43 PM
So is it a really big job to remove the intake? I'm reasonably Mechanically inclined but, I might be a little nervous when it comes to that job.

I'm not having any problems yet, but, perhaps when the time comes I just wondered how big a job it was?

07-25-2007, 02:48 PM
It's the furthest I've ever been into an engine, just to give you an idea of my limited experience and it wasn't really hard. I mean it takes some time and you have to unplug a few things, remember where they went, etc. You can do it without unhooking the fuel lines but it would be easier to unhook them, which requires a special tool. In the end I wish I had rented one to make it a little easier. But if you're mechanically inclined, you can do it.

07-25-2007, 03:43 PM
Its not a difficult job and the fuel line tools can be purchased for a few bucks at any auto parts store.

The intake is pastic so dont try and kill the intake bolts, they actually bottom out before you can over torque them.

The knock can be tested before you take the intake off. Take the plastic motor cover off and (standing at the grill) on the right side of the intake toward the back there is a plug that comes from the back side of the intake and joins in the harness. Its clipped to the intake and has a blue retention clip. Its a 2 wire plug.

This is the harness to the 2 knock sensors. Unplug the knocks there and drive the truck. If the rear knock is bad due to the moisture problem then the PCM will stop looking at them once there unplugged which will put the timing to a baseline. If no change in the knock happens its not the knock sensors. Might want to check a clogged fuel rail then!!!! (HINT HINT)

If you do pull the intake make sure you get the updated one from GM. The old one would shrink and suck air on cold start ups. Oh and dont forget to take the foam inserts out of the intake before you re install it.

07-25-2007, 04:13 PM
Yes, Bank 2 is the rear sensor. You do have to pull the intake off, as they are located underneath, and screw directly into the top of the lifter valley. The intake gaskets can be reused as long as the silicone bead is not flat. When I changed these on our '99, and also on the '02 which I rebuilt the 5.3 on, I used silicone on the plastic cover, both on the outside of the cover and also on the inside where the wire passes through.

07-25-2007, 06:57 PM
Forget my answer, it appears the mods don't want my business.

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