Which Knock sensor is P0327?

[Matthew Jeschke]

First there are two knock sensor fault codes. One is for Bank one, the other for Bank 2. However, both sensors are located directly in middle of the valley. We're getting code P0327, anybody know if that's the front knock sensor or the rear knock sensor and which sensor is which on the harness?

Background, my buddy has a 2005 Z71 Silverado. It's ABSOLUTELY cherry. He got a knock sensor code and asked if I wanted to do the repair. I'm not a insured mechanic though and said best he take that to a shop. I picture myself dropping something down into a cylinder during repair and making a nightmare situation...

Well, he took it to the mechanic, twice and they couldn't fix the issue. First time they replaced the sensors but not the harness. Second time they replaced the harness. I'm not sure what they diagnosed though...

I started by hooking a oscope to the harness and exciting the sensors (knocking on the block) both sensors generate a signal.

I think his issue is with the PCM and or PCM side of harness. However, I'd love to figure out WHICH wire to focus in on. I cannot figure out which sensor is for P0327.

On a side note I logged data with HP tuners VCM scanner on his truck. I'm shocked to see it pulling as much as 8 degrees of timing at 1800 to 2000 RPM. Something doesn't seem right to me there. For comparison, my 6.0L I built pulls NO timing / registers no knock w/ 87 octane fuel even, unless I start messing with the timing.

 

[Doubeleive]

well all the timing stuff aside
it's always best to do BOTH knock sensors and new harness and use OEM parts at the same time, otherwise you are back in there again as is probably the case now
do not over tighten them torque to spec only they can break easily. and put sealant around the top edge to keep water intrusion from happening.
it's not a hard job at all just follow procedure
these guys nailed it in there youtube video, follow what they do and you can't go wrong, unless you do like I did and mistake ftlbs for lbs and snap a bolt off in the head

 

[Matthew Jeschke]

Both sensors and harness are new. I am trying to determine which wire in harness or pin on pcm is faulty.

 

[Doubeleive]

Both sensors and harness are new. I am trying to determine which wire in harness or pin on pcm is faulty.

this guy goes over troubleshooting it and in the description is a written process

 

[ScottyBoy]

I replaced both mine a few years ago on my 2001. I used AC Delco sensors, and a Dorman wire harness. Took me two days the do the entire job, but part of that is because I was being so picky. While I had the intake off I spent a few hours cleaning it. The inside had a lot of oil residue everywhere. Between a bunch of degreaser, a toilet brush, water hose, air nozzle, and a leaf blower, I eventually got it looking like brand new. Then I ended up cleaning the intake valley plate completely as well. Other than all the extra time cleaning, it's actually not that bad of a job. I'd say a novice could replace it all in an afternoon. I'm sure a pro can do it in about an hour. Honestly, I'd probably pull the intake and replace the harness again. Then after you replace it, do some testing on the wires while you still have the intake off. Do some continuity tests between the PCM and the sensors. If you live someplace up north where it snows, then look at EVERY junction/plug for any green crusty corrosion.

 

[Matthew Jeschke]

The sensors are new, along with the harness... The shop replaced them both. I also validated the sensors with an oscilloscope. They create current when I tap on the block.

I have two somewhat unrealted questions:

1. I need to know which sensor is associated with P0327.

2. It hasn't seemed to throw the code since I disconnected and reconnected the harness to measure the sensors. However, I logged data with HP Tuners VCM scanner (somewhat like tech 2 scanner). It's registering knock between 1800 and 2000 RPM at which point it pulls up to 8 degrees of timing. That's a LOT of timing. For comparison, my truck / PCM doesn't pull any timing at all (see signature for specs), and his truck is all stock 5.3L.

 

[THarber]

Make sure nothing is loose on the engine block, ie engine mounts, exhaust, etc. The sensors pick up basically sounds, so any type of vibration might set them off. If you are not hearing any spark knock, use your HP tuners to decease the sensitivity of the sensors, or temporarily turn them off. If you used anything other than AC Delco sensors, change them out. Knock off versions always cause issues.

 

[Matthew Jeschke]

I've never turned off knock sensors haha

That said nothing is loose, so far as we can tell.

However, I definitely wondered if they used authentic AC Delco parts at the shop where they replaced them. If they are slightly different electrically they'll create false knock.

Unfortunately, my friend didn't know what they put on at the shop.

Backstory, my friend asked if I wanted to do the repair for him. However, I'm not insured. I picture myself dropping a bolt in the cylinder on a job like this and thought I'd rather have a shop deal with that headache. Although I've replaced these before and is only time consuming, not that hard. Unfortunately at this point I kind of wish I'd just changed them for him.

 

[Doubeleive]

I've never turned off knock sensors haha

That said nothing is loose, so far as we can tell.

However, I definitely wondered if they used authentic AC Delco parts at the shop where they replaced them. If they are slightly different electrically they'll create false knock.

Unfortunately, my friend had no clue what they put on at the shop.

Backstory, my friend asked if I wanted to do the repair for him. However, I'm not insured. I picture myself dropping a bolt in the cylinder on a job like this and thought I'd rather have a shop deal with that headache. Although I've replaced these before and is only time consuming, not that hard. Unfortunately at this point I kind of wish I'd just changed them for him.

no warranty? no way to call and ask what brand they used? no receipt?
in that 2nd video I linked in the comments it seems to be a common issue with none resolved in the comments but one person did mention adding a ground.

 

[Matthew Jeschke]

Yeah I encouraged he find out what the part is they put in.

Sounds like they didn't replace the harness. He took it back when it wasn't working and oddly enough they had only replaced the sensors and not the $15 harness or whatever that costs. They took it apart again and replaced the harness. I get the impression they didn't do much troubleshooting, only assumed it was the sensors.

I HATE taking stuff apart until I can fully isolate the fault. Pretty easy to do with knock sensors.