I'll try and make this as short as possible.

Bought the car with mods in sig....and car already had a tune of some sort since it doesn't throw the typical LT codes. Mods and tune have been on car for 5+ years.

1. Battery dies initially. I replace, no problem.
2. Few days after replacement it throws P0416 code. I replace passenger side check valve and it goes away. Great...right??
3. I install NGK TR55 plugs and MSD wires soon after. After install I wash up the engine bay a little with hose water and a degreaser.
4. A few days after, I throw a P0327 code and P0416 code (again). Obviously, I'm more worried about the knock sensor code.
5. Around this time I notice a little more vibration/rattling...under the center console a little when in Drive and slowly moving or stopped at a light, although slightly noticeable under load. Goes pretty much away in Park.
6. Eventually, get around to having a shop replace the knock sensors. I supplied the sensors (GM wholesaler online, so OEM) because I originally planned to do it myself. They said they couldn't guarantee the parts if malfunctioned and would have to charge labor again if they were the culprit. Though, they did supply the wiring pigtail and did perform the bulletin RTV sealant dam.
7. Everything seems to be great after I get it back. Power seems to be more instantaneous and smoother. They did a coolant flush and oil change as well.
8. I drive it for a week or so, no problems. Although, that rattle/vibration is still around now and then and only perks it head once the car is warm.
9. I put in the first tank of new gas since being fixed. 93 octane from QT. The next day getting on the highway going to work.....ding ding....there's that dang SES light again. My heart literally sank.
10. Finally scanned it today at Autozone. It's the P0327 code...AGAIN. And I have noticed a return of slightly less power. Doesn't seem to be knock, just the timing retard with the light being on I suppose.

Can anybody give me any insight?!?!?!?! I've searched all the boards.

Could the high flow cats be clogged and on there way out, thus causing vibration and all the air system and knock sensor codes???.....Could the LT's be causing vibration, thus the code???

I'm losing patience. The car had none of these creeks and moans when I bought the car. But right after the knock sensor code came on originally, the under console rattling started. Only to be cure by Park or a cold start.

I'm really sour on the car right now. I sold my uber-reliable Chevy Silverado of 3 years to go back to the impracticality that is a Camaro/F-body. I held off from getting my dream car for too long, so I broke down and bought it....and this is what I get.

 

Come on...anyone have any insight? I paid over 600 bucks for this knock sensor overhaul, and it just comes back. I can't understand it.

 

Search that code on the net. Most seem to find that if sensors are good then it's wiring or PCM problem.

 

Wiring, as in where???...after it leaves the intake and those pigtails?

And PCM, I'm assuming you mean there could be a problem with the tune the car had on it already?

And believe me....I've been doing some searching....the only thread I've found on here that resembles my problem is a guy with a 98 SS that was having the p0327 in conjunction with air system problems and cat problems. And since I don't have rear O2's, I was thinking my car wouldn't be able to tell me if a cat was going out.

 

www.gearchatter.com/viewtopic9031.php

If you haven't seen it, this is what the book says. There are a couple things you can check yourself and shows the wiring schematic.

 

I read the gear chatter stuff. Very detailed. I obviosly can't do this stuff myself. I don't have the scan tools/hptuners software. I'm thinking my best bet is to just take it to get dyno tuned at a legitimate shop and see what they come with on the software. Think I'm on the right track here?

 

Before I try the dyno tune route I'm going to put some straight pipes in place of the cats to stop the vibration/rattling coming from a possible bad cat or two. Since I already replaced the knock sensors, pigtail and all, I'm thinking I might be getting some false knock.

 

I finally had a chance to listen underneath the car a few minutes ago. The rattling seems to be coming from the driver side cat's heat shield almost resting up against the brake lines going up the center of the car. I had to rest something on the gas to keep the rpm's at 900 or so....to get the sound I was hearing. I have no clue if that would be enough to set the sensors off.

Another weird thing was the car seemed to drive really well on the way home from work....with the SES light still present. It was very smooth through the band and was pulling at least if not more hard than any other time I've had the car so far. I'm wondering if maybe it is a bad batch of gas.

I still have 3/8's plus of a tank...so I don't know if I want to run it down some more before I put a new tank in....or if I'll just do it now and put a fuel system cleaner in.

 

Don't assume, ever. I was not talking about the tune I was refering to the hardware itself. PCMs do physically fail. Pin connections, cracked connections inside, the processor itself. Don't ever assume that any part new or old is bullet proof.

Daughter had a Corsica a few years back that the cooling fans wouldn't come on. Checked everything out and all was fine, wiring was good, relays worked, direct power to the fans and they came on. Changed out the ECM and viola the fans started working again.

Now this doesn't mean that you should go out and change the PCM out. It just means trouble shoot and test to find the real problem. And don't ***-U-Me.

 

If the knock sensors are picking up detonation, they will not set a DTC. If they pick up false knock from another source, they will not set a DTC. The only way they will set a DTC would be due to some sort of electrical failure.

$600 for knock sensor replacement? WOW! That's a ~$200 job. If I were you, I would pull the intake myself and check to see if they were even replaced. You might be surprised at what you find!

 

Well, that definitely clears some of my previous thoughts up. Pretty much narrows it down to some sort of connection like you say. $600 is a ton, and I sorta regret doing it, but I had just sold my truck, started up work again after deployment and needed my Camaro to be my daily driver. I knew the code it was throwing and knew I had gotten water on the intake when cleaning and soaked it. I thought it was pretty cut and dry....soaked sensor, needs replacement, replace pigtails, both sensors and have them do it since I didn't have the time. And my mechanic brother in law didn't have time either.

They even told me it the front sensor was soaked. Said they cleaned it up dried it off and put new sensors in, new wiring pigtail in, and new intake gasket. I'm really at a loss as to why the same code came up a week after getting fixed. I would call them up and say hey fix this, but they couldn't guarantee the work since I bought the sensors myself and they didn't run their own diagnostic scan (my fault for not paying the extra for the insurance there). I suppose they could have done it wrong and that would be there fault but I don't want them to get in there and say bad sensor and I pay for labor all over again.

 

Pull the intake yourself. It's not hard or time consuming, and requires very basic handtools. There are step by step directions everywhere! Try ls1howto.com

 

I'm going to let them scan it this weekend. That way they can tell me it is either the sensor itself...or the pigtail. Hoping the scan can point to which one it is, that way they don't have take off the intake again. Plus, if it is the wiring pigtail they should be liable since it's their part. If they have to take it off again, and I'm liable for the labor again, I WILL do it myself.

I'm also planning on calling Performance By Joe, here in St. Louis. I'm going to see what they can do about a tune. I want them to tell me if it has a tune already, or if it was just a simple hand held one. I'm betting it was hand held. I ordered some non-catalytic converters online (straight through stainless pipe that looks exactly like a cat) to take care of my rubbing problem and any future cat failure.

 

I finally got the same shop to take a look at it better. They went through some procedures and tapped on the intake and said both sensor were reading the tapping. So their conclusion was that the sensors were working fine and that either the PCM had gotten water on the inside or the y-pipe touching underneath was setting a false knock sensor code off. I don't know why false knock would set off another p0327 instead of another knock sensor code.

Either way, I went and got straight pipes (cats that have straight pipes) put in place of the cats. The exhaust guy did a decent weld job but he ended up making the y-pipe bang pretty seriously on the driver side frame just past the header collector. And I NEVER thought I'd be doing this, but I have a crushed soda can and some cardboard strapped to the pipe to stop the banging. So I have to go back to get him to fix that....maybe heating up the pipe and flattening it out a little.

Hopefully, after I get the pipe from touching the SES light and p0327 code will go away and I can then get it tuned....or maybe the tune will fix it, who knows because I sure the hell don't.

 

I know I said it before. The PCM will NOT set a DTC because of false knock. It is there due to an ELECTRICAL fault.

And a soda can with some cardboard? I've heard lots of remedies for the banging y-pipe issue, but this is new to me. If you do not want to properly fix the problem with new engine mounts, a worm drive hose clamp with some EGR/emissions hose on it works well.