SES Light Came On - P0327

[yonyon]

Originally Posted By: RoGuE

Also, I have some black high temp RTV from couple years back. How would that work to seal up the knock sensor covers to make sure moisture doesn't get in?


Instead of using the RTV to try sealing the boots to the cover, use it to make a sort of a dam around the holes so that any water on the valley cover runs around them. This way air can still get in and out, which is good.

 

[mattd]

get 2 knock sensors, as well as connectors. rear one usually rots away and the front one is fine, but i always do both. you'll laugh once you get the intake off.

Make sure you correctly torque intake bolts. The job is overall pretty easy.

 

[RoGuE]

Originally Posted By: yonyon
Originally Posted By: RoGuE

Also, I have some black high temp RTV from couple years back. How would that work to seal up the knock sensor covers to make sure moisture doesn't get in?


Instead of using the RTV to try sealing the boots to the cover, use it to make a sort of a dam around the holes so that any water on the valley cover runs around them. This way air can still get in and out, which is good.


It's funny you say that, as I just saw before reading your response that GM has a TSB that suggest to build up a dam around the knock sensors.

While I have this thing opened up, what's the best method to clean up the whole manifold as well as the little bit of access you have to the heads?

 

[dailydriver]

Originally Posted By: RoGuE
In general, are the MAP, OP Switch, and CPS hard to replace? I found a guide for the OP switch elsewhere... that doesn't seem hard and saw someone was even able to do it with the manifold still on, though I could see how it's a lot easier without it.


I TOTALLY forgot that this is a SUBURBAN you are working on, and was referencing MY car, which has almost HALF of the LS1 UNDER the cowl (for weight distribution purposes)!

You might just be able to access ALL of those other components with the intake manifold IN PLACE on that truck (I've NEVER looked under the hood of one), if they are currently functional, and you want to hold off on them.

I had the same exact code, and replacing the knock sensors AND the harness/connectors for them eliminated it.
To check for problems in the line to the ECM (AFTER where the harness conects to it); I have no idea.

 

[yonyon]

Originally Posted By: RoGuE

Edit: I forgot to ask, does anyone know what the procedure is to check if the fault is in the wiring or the knock sensor itself when using a multimeter? My Haynes book doesn't even mention a procedure.


If there's a problem in the wiring it'll almost assuredly be in the little jumper harness that goes from the top of the intake to the sensors. You'll have that harness off the car anyway after you take the intake off, so it's a simple matter of checking continuity end to end. It will be obvious how to do that when the thing is in front of you.

To check the rest of the wiring, which probably isn't worthwhile, you do not need to remove the intake. If you feel a need to check for a wiring problem between the jumper harness and the ECU, you'd have to check continuity end to end (dig up a PCM harness connector pinout) and also verify no short to ground and no short to power unless you have a code for one sensor and not the other. In that case, meaning specifically you have P0327 or P0332 but not both you can cheat a bit: simply use a paperclip to jumper (by backprobing) the connector for the subharness across the two signal wires and then clear DTCs and drive the truck normally for a couple of days. If the code comes back the problem is in the main harness or the ECU or your paperclip fell out. If the code does not come back the problem is a bad knock sensor or subharness.

 

[RoGuE]

Originally Posted By: dailydriver
Originally Posted By: RoGuE
In general, are the MAP, OP Switch, and CPS hard to replace? I found a guide for the OP switch elsewhere... that doesn't seem hard and saw someone was even able to do it with the manifold still on, though I could see how it's a lot easier without it.


I TOTALLY forgot that this is a SUBURBAN you are working on, and was referencing MY car, which has almost HALF of the LS1 UNDER the cowl (for weight distribution purposes)!

You might just be able to access ALL of those other components with the intake manifold IN PLACE on that truck (I've NEVER looked under the hood of one), if they are currently functional, and you want to hold off on them.

I had the same exact code, and replacing the knock sensors AND the harness/connectors for them eliminated it.
To check for problems in the line to the ECM (AFTER where the harness conects to it); I have no idea.


Okay, I was able to verify that the MAP, Camshaft position, and oil pressure switch are all accessible without the intake being removed. The CPS is EASIER with it off, but not necessary.

FWIW, here is a pic of the engine:


Originally Posted By: yonyon
Originally Posted By: RoGuE

Edit: I forgot to ask, does anyone know what the procedure is to check if the fault is in the wiring or the knock sensor itself when using a multimeter? My Haynes book doesn't even mention a procedure.


If there's a problem in the wiring it'll almost assuredly be in the little jumper harness that goes from the top of the intake to the sensors. You'll have that harness off the car anyway after you take the intake off, so it's a simple matter of checking continuity end to end. It will be obvious how to do that when the thing is in front of you.

To check the rest of the wiring, which probably isn't worthwhile, you do not need to remove the intake. If you feel a need to check for a wiring problem between the jumper harness and the ECU, you'd have to check continuity end to end (dig up a PCM harness connector pinout) and also verify no short to ground and no short to power unless you have a code for one sensor and not the other. In that case, meaning specifically you have P0327 or P0332 but not both you can cheat a bit: simply use a paperclip to jumper (by backprobing) the connector for the subharness across the two signal wires and then clear DTCs and drive the truck normally for a couple of days. If the code comes back the problem is in the main harness or the ECU or your paperclip fell out. If the code does not come back the problem is a bad knock sensor or subharness.


Wow...that sounds like it's more trouble than it's worth. I'd definitely be more inclined to just replace the knock sensors and connectors and hope for the best...

 

[Merkava_4]

Originally Posted By: RoGuE
How critical is using a torque wrench for this job?


That depends on whether any gaskets are involved. Usually gaskets are torque sensitive.

 

[yonyon]

The only gaskets involved are the sort where there's a squishy rubber seal inside a hard plastic frame. Bolt torque won't impact seal squish unless they're left so loose that they're going to fall out anyway or so tight that something breaks.

 

[dailydriver]

Originally Posted By: yonyon
The only gaskets involved are the sort where there's a squishy rubber seal inside a hard plastic frame. Bolt torque won't impact seal squish unless they're left so loose that they're going to fall out anyway or so tight that something breaks.


Yes, these composite manifolds WILL crack if the mounting bolts are over-torqued!

 

[yonyon]

Don't do that.

Edit:
Basic torque wrenches are a lot cheaper than intake manifolds. Nut drivers are even cheaper but could lead to under-torqueing. Either way, plastic intake manifolds really are almost as fragile as aluminum ones and should be protected from gorilla-arms.

 

[RoGuE]

I finally got this done today. It took...a lot longer than I thought it would. The sensor in the front, which I assume was giving the fault code, was completely corroded and submerged completely in water. The water had turned into a clay colored liquid with the consistency of paint.

Got it all back together with only one part casualty. The hard plastic hose that goes to the PCV broke. I wrapped it in some duck tape for now. One of the knock sensor connectors broke as some as I touched it because it was so brittle, but I had a replacement harness anyway. Here are some pics:

The remains of one of the knock sensor connectors.

The corroded sensor and the paper towel I used to dry up the hole.

Both of the old sensors.

 

[dailydriver]

That's the same CMP, and oil pressure switch as on my engine.

Are they both TOTALLY under the cowl with the intake installed?

 

[RoGuE]

If I were to literally lay right on top of the intake, I could probably get to them by feel alone. It it helps to visualize how much space there is under the cowl, the MAP sensor is completely accessible without removing the intake.