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How to identify my engine so to get the proper knock sensors.


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Hi people. I'm new to this forum and hate to ask for help, but idk what to do.

I purchased an older truck from an auction a few years ago. I hardly use the truck, but for moving gravel or quads, I just needed it since I can't do this with my VW bug.

The problem started with realizing after I purchased the truck that there's been some rebuilding, and for a while now, I've been getting knock sensor codes (ie. low input P0332 and P0337). I changed them out last year with some lower end sensors + harness, but the codes returned, so I changed them out again recently with ACDelco and a new harness, and again the codes are reappearing.

Now I'm wondering, although the Sierra 2500 (2006) came with a 6.0 vortec, is it possible that this engine has been swapped with a 5.7? I saw 5.7 written under the hood when I first bought it, but never thought much about it, and now I'm just not sure.

I've looked on the front of the (leftside) head, but there was only a 4 letter code that didn't id anything. There were some numbers on the cylinder, but again, nothing comes up doing a search for them (ie. zero hits on google). I've heard that the engine number should be stamped somewhere near the rear of the engine, but I can't see anything. So where should I look for the engine's serial number?

I know the engine is a vortec engine (as the plastic cover above the manifold indicates), I just want to make sure. If this is a 6.0, then maybe I will need to look at the PCM 'knock module'. If this is actually a 5.7, I think I may need to order different knock sensors (?) I'm not sure and could use some help.

image.thumb.png.37f37604ab75382f01d74945fd9f9cc1.png

This is a picture of the leftside engine in front of the cylinder head. I think it reads D224? I'm not sure.

Edited by SLAM BAM
adding picture and number
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If its a 99-06 LS the VIN pad is on the left rear of the block on a flat spot just behind the left head.  

 

All the Gen 3 LS that I can tell use the same knock sensors (12589867) and harness (12601822) and are under the intake manifold so LS1, LS6, 4.8, 5.3 and 6.0.

 

Gen 4 LS the knock sensors moved to the sides of the block.  

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Thank you guys. It dawned on me last night that the intake manifolds would probably substantially different for either 5.7 or 5.3. Maybe they replaced the hood? The only reason I know this is I looked up the VIN history; says the truck was stolen in 2014 (!) and then written off? idk, works good except these knock sensors.

If then the knock sensors, I suppose I need to look at the PCU next? There's a 'knock module'? I'll check the connectors and see what's up. I did drive it last summer for about 800 miles without a problem (with the older knock sensors) but they showed up. Since I've changed them, I check the resistance (~99kOhm) and say some mV show up doing a tap test. Seems like a recurrent nightmare with these vehicles.

I'll try to look behind the left side. I was looking on the rear right side... now I understand why I didn't see it.

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On 11/25/2023 at 11:03 AM, SLAM BAM said:

Thank you guys. It dawned on me last night that the intake manifolds would probably substantially different for either 5.7 or 5.3. Maybe they replaced the hood? The only reason I know this is I looked up the VIN history; says the truck was stolen in 2014 (!) and then written off? idk, works good except these knock sensors.

If then the knock sensors, I suppose I need to look at the PCU next? There's a 'knock module'? I'll check the connectors and see what's up. I did drive it last summer for about 800 miles without a problem (with the older knock sensors) but they showed up. Since I've changed them, I check the resistance (~99kOhm) and say some mV show up doing a tap test. Seems like a recurrent nightmare with these vehicles.

I'll try to look behind the left side. I was looking on the rear right side... now I understand why I didn't see it.

 

 

4.8, 5.3 and 6.0 use the same intake.  The car applications use a shorter one so LS1, LS6 aka the 5.7 LS engines.  

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On 11/27/2023 at 7:20 AM, newdude said:

 

 

4.8, 5.3 and 6.0 use the same intake.  The car applications use a shorter one so LS1, LS6 aka the 5.7 LS engines.  

ok, so that brings me back to trying to id the engine the hard way. The knock sensor thing keeps coming back, so I will have to pull off the intake again. Maybe I'll be able to see the numbers in the back once I take it off. If not, I'll have to take off the bracket in the front of the engine to verify.

Needless to say, if the 5.3 and 6.0 uses the same KS, then the problem isn't the wrong KS. I've read that there's a lot of bad KS out there and that ACDelco is no exception. I'll reinstall and clean out the thread and hole in there. I'll also have to look at the connection to the ECM.

I noticed that the console lights are shorting out, associated with the dimmer switch. Could this have something to do with it?

 

gremlins 😕

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22 hours ago, SLAM BAM said:

ok, so that brings me back to trying to id the engine the hard way. The knock sensor thing keeps coming back, so I will have to pull off the intake again. Maybe I'll be able to see the numbers in the back once I take it off. If not, I'll have to take off the bracket in the front of the engine to verify.

Needless to say, if the 5.3 and 6.0 uses the same KS, then the problem isn't the wrong KS. I've read that there's a lot of bad KS out there and that ACDelco is no exception. I'll reinstall and clean out the thread and hole in there. I'll also have to look at the connection to the ECM.

I noticed that the console lights are shorting out, associated with the dimmer switch. Could this have something to do with it?

 

gremlins 😕

 

 

Check any grounds in the engine bay (I think one is on the back of the block?) and the ground strap going from the hood to the firewall.  

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1 hour ago, newdude said:

 

 

Check any grounds in the engine bay (I think one is on the back of the block?) and the ground strap going from the hood to the firewall.  

Will do. I also ordered some electrical contact cleaner, should be here in a few days. I will check the electrical connections (and ground) before continuing.

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  • 2 weeks later...

Looks like the main ground has been moved and is attached behind the exhaust manifold. The one to the hood wasn't hooked up, but I hooked it up. I don't understand the reason for having the one on the hood.
Anyways, I cleaned the PCM connectors and applied dielectric grease, but I still get the low/no voltage codes.
I reviewed the source from where I purchased the ACDelco KSs and there are some 1-star reviews stating that these are knock offs and don't work right.
I did check the resistance, which was in range. And tapping on the manifold did produce voltage.
I will need to change the sensors using the dealership's parts.
This will be the third time doing this.

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  • 2 weeks later...

I purchased some knock sensors from the dealership. These each cost ~$175. I went to remove the old KSs and they just spun around, so I twisted them hoping to pinch the seal, and instead broke them. I needed to carefully drill, and then extract using an extractor tool. They weren't in there too tight, but the assembly spun, so it is what it is.

You can see the picture where the KSs snapped. This happened to both the sensors, but I did remove them both without any more issue. I was able to tighten the new sensors to the appropriate 15 lb/ft torque.

I've had no other issue since I've changed the knock sensors.

 

You can see in the picture that the older sensors look authentic, but I think purchasing knock sensors should be done via the dealership. Lesson learned after getting burned.

 

Oh, and I was able to copy one of the engine codes when I had the intake off. Seems like it is a 6.0 afterall.

 

Thank you for the help @newdude

 

100_1356.JPG

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