When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hoping someone here will be able to help me out, half of the guys on the truck forums don't know what a knock sensor is.
My 2000 Suburban with the 6.0 LQ4 (200k) is giving me two knock sensor codes for bank one and two. I recently replaced the knock sensors after getting the code P0332. My rear sensor was corroded like a lot of engines and there was a lot of crap under my intake. I changed the knock sensors and harness and rtv'd around them. I've cleared the codes, but they come back almost immediately. I don't have a check engine light, they are stored codes. I've had the 2 codes for over a week now.
Would it matter if the knock sensor harness is installed the wrong way? I'm 90% sure I installed it properly, since it was the only way the cable would reach, but if it makes a difference I could try switching the wires.
My truck idles fine and I have good vacuum, but it seems to be missing some power. Only upgrades are CAI and headers. I can hear some hissing and slight tapping, but the truck has 200k on it and I'm pretty sure that is the intake and rusty muffler.
Thanks for any help in advance.
Edit: I'm halfway through 40 gallons of 93 octane, so I don't think it's a problem with low quality fuel.
Last edited by Suburban2500; Feb 29, 2016 at 08:49 PM.
Did you use AC/Delco parts and install them with a Tq wrench, 16~18 ft/lbs? If setting P0327 or P0332, PCM will preemptively pull timing, ie the missing power.
I used 1aauto parts, don't seem to be bad quality. Yes, torque was 190 in/lbs.
If I can't find anything else out, I will get the ACDelco parts and genuine
GM harness. Hopefully I get some more advice, since I really don't
want to replace something that's working fine.
Anyone have any bad experiences with 1A Auto parts? They have a 60 day guarantee so I can send them back and spend $30 more on ACDelco if that is the problem, but would like to try other things before tearing into my intake again.
Last edited by Suburban2500; Mar 1, 2016 at 08:59 PM.
Reason: Bad cell phone typing.
Still have both codes, hoping someone else has an idea so I don't have to replace brand new parts. Half of my wiring connectors felt like they were going to break getting the intake off the first time.
You could turn the codes off with tuning software/cable. I do it a lot for customers that have changed them and still set codes. The sensors usually still work for detecting knock when they fail the diagnostic. Setting the codes to No Error Reported does not disable their function.
Thanks for the tip, unfortunately HPTuners isn't in the budget just yet (plan to get soon though.)
1A Auto is giving me a refund without having to return the parts, so I will order the ACDelco knock sensors and better harness as soon as that is processed.
Although I'm fairly sure this will fix my problem, if it doesn't, who could I contact about getting a tune to turn the codes off and also, if possible, delete EGR? (Found a lot of crap in intake from it)
Edit: Blackbear won't delete EGR unfortunately.
Last edited by Suburban2500; Mar 7, 2016 at 05:13 PM.
So you removed the OEM knock sensors (because of codes?) And installed new ones, and the same codes came back still?
-And, it seems to be missing power? (as if the knock sensors were disabled/ causing limp home timing)
Lets see. If the knock sensors were good to begin with, it explains why you are still getting the same codes after changing them. Following this logic, it leaves the harness, and the ECU. I would change/fix/wire/inspect the harness first, try wiring it directly to the computer for example ( go around all the OEM wiring, just look at the FSM schematic and find the knock sensor wire(s) should be very few of them, tap into them and run the wires directly to the sensors temporarily for diagnistics). It sounds like the ECU just isn't "seeing" them due to the harness issue.
So you removed the OEM knock sensors (because of codes?) And installed new ones, and the same codes came back still?
-And, it seems to be missing power? (as if the knock sensors were disabled/ causing limp home timing)
Lets see. If the knock sensors were good to begin with, it explains why you are still getting the same codes after changing them. Following this logic, it leaves the harness, and the ECU. I would change/fix/wire/inspect the harness first, try wiring it directly to the computer for example ( go around all the OEM wiring, just look at the FSM schematic and find the knock sensor wire(s) should be very few of them, tap into them and run the wires directly to the sensors temporarily for diagnistics). It sounds like the ECU just isn't "seeing" them due to the harness issue.
Alright, I'll give that a try if the new parts don't help.
I was only getting one low voltage code for the rear knock sensor, which I think was caused by the corrosion on it. In my (albeit somewhat limited) efi experience, one bad knock sensor is usually a faulty one, two bad ones are another engine problem. So I'm assuming the original harness, wiring, ecu was alright to begin with. The power was the same before I replaced, but it hasn't always been like this.
The new harness didn't appear to be broken, but it wasn't insulated well and was shorter than the factory part. It's annoying how hard to get to the knock sensors are, makes it really difficult to diagnose since there's no way to run the engine and have access to them.
I'm hoping that the cheaper sensors I bought were not quite right or broken in shipping, or the harness is wired incorrectly, but we'll see when the new knock sensors arrive. Seems like a lot of people have similar problems with any parts other than ACDelco. Probably should have sprung for the ACDelco parts to begin with, but 1Aauto didn't seem bad at the time. Figured it was better than eBay.
Alright, I'll give that a try if the new parts don't help.
I was only getting one low voltage code for the rear knock sensor, which I think was caused by the corrosion on it.
Ok, I see now. Yes this sounds right. SO you are saying its like you installed incompatible sensors. Have you thought of using "used" OEM knock sensors, instead of "new" sensors?
Just an update to help out anyone else having this problem:
Replaced the knock sensors yesterday with ACDelco parts, no codes so far and truck runs much better, feels quicker than when I bought it.
I think part of my problem was there was a lot of dirt in the rear knock sensor hole that I didn't catch last time. I have no idea how so much have gotten in, since it was all below where the sensor usually sits. My truck is fairly high up so I had to climb into the engine bay to even see it. Probably scooped out about a tablespoon of dirt, then hit it with degreaser and air until it was completely clean.
Dorman harness was identical to 1A's part other than packaging, which I don't really like due to lackluster shielding on the wires, hopefully it holds up though. I think my problem with the harness reaching was due to it getting stuck somewhere on the intake.
No, that part is just the rubber which squishes down anyways. Wouldn't think it would matter if it's compressed. I'm pretty sure they're not TTY either. No leaks here. Just followed the torque sequence and all was good.
Last edited by Suburban2500; Mar 28, 2016 at 06:14 PM.
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.
7 Most Reliable High-Performance Engines GM Has Ever Built
Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
Replaced Knock Sensors, now getting 2 codes. 
