Knock Retard not reporting

Hello everyone my name is Preston and I am new to HPTuners and new to the forum so I will start off with the detail and what I have tried so far. Vehicle is a 2005 Chevrolet Suburban 5.3l 4wd Vin Z L59 engine and P59 pcm. I recently pulled the engine and replaced all the leaking gaskets top to bottom with exception of the head gasket as I didn't want to go that far into the engine. When I did all the gaskets I replaced the knock sensors and harness because the existing ones looked tired, but they never gave me issues. Also did new spark plugs and wires. Mods I've done during this were SacCityCorvette billet oil diverter, Summit SUM-8701 cam, Pac-1218 springs.

Cam specs: Stage 2 LS Truck Swap Cam, 218/227 112+2, .523/.524 Lift

Now on to the issue I've been having. On initial start-up I obviously had issues with idle, also set a P0327 and P0332 I think they were. Got the initial idle set so I could move on. Tuned the MAF first then moved to the VE table. After this the P0327 and P0332 went away, but I acquired a P0300 random misfire code at idle that I came to the conclusion was because of the cam so I adjust the misfire detection and got it under control. At this point I notice some weird things with acceleration and did some adjustment on Torque Management and smoothed the acceleration.

Finally I got to tuning the timing table. I started to add in timing and saw no Knock Retard at points where I'm sure there should have been some. At one point I chose a point in the rpm range and advanced it by 14 degrees and could audibly hear knock, but still showed nothing on the table. When I say audibly I mean I could hear it through a DIY set of det phones I made for another project that does not have a knock sensor factory. At this point I contacted HPTuners to see if it was in the software and tech support said everything looked good with my scanner setup, so I set out to checking the knock sensors. Both sensors ohm out fine and with a DVOM I do get a change in AC voltage. I know I should be checking them with a scope, but that is all I have personally. I will note the knock sensors are not OE and I have seen people say they had issues with aftermarket sensors. I don't believe that is my issue though. While checking the sensors I also wanted to check the harness to the PCM, but I can't find a reliable wiring diagram. In attempts to eliminate variables I decided to load my very first tune just after get the idle set so I could drive it without it trying to die when coming to a stop or during low speed turns and unplugged the knock sensor harness where it plugs into the main harness at the top of the intake manifold. I have completed no less than 10 drive cycles and show no DTCs for knock sensors in stored or pending which I find odd.

So at this point I did some searching and found a module called a Knock Control Module part number ACDelco 216-64 and several places show it to fit my vehicle. I cannot find a location or a wiring diagram that depicts it or even mentions it. In the part description for that parts it sounds like the knock sensors report to it and it send a signal to the PCM to set a code. So my conclusion is that part has fail so the PCM never gets a signal to give a code for the knock sensors. Any insight from you guys into this problem wold be greatly appreciated.

Thanks in advance,
Preston.

Never heard of a knock control module. The knock sensor harness goes straight into the PCM. I tried to cross that number and came up with it fitting late 90's 4.3 vortec engines.

Post a log if you want.

You can even smack the block with a mallet, it should show some knock in the channels.

Thanks for the reply. I have tried tapping on the block and to see if it reported knock. I did that with both VCM scanner and also a OBD2 scanner that shows live data, neither of which showed any knock. Also tried it with the old knock sensors and harness off of the engine but still grounded to it to the same results. At this point I think it is one of 3 things, either the engine harness to the PCM has a short to ground which somehow reads the perfect amount of resistance for the pcm to not throw a code(which is unlikely), the pcm itself is bad(also I think is unlikely because it threw knock code prior), or in writing the tunes I somehow disabled or corrupted the portion of the tune that handles knock functions.

I'll include my tune when trying to induce the knock, the log from that drive and also my vcm scanner channel, charts, graphs and layout.

Thanks,
Preston

I have finally had the time to test the vehicle again and the wiring tests fine as do the knock sensors. I decided to make some adjustments on the tune in the knock sensor section. I adjusted the Tip In TPS, Tip In RPM, and vs. RPM vs. Cyl under the knock Sensor Level category to what I assume is the most sensitive they can be without maxing out the table. I got a log with this setup and recorded knock. Would anyone have any ideas as to why I would need the sensitivity set so high to achieve this?

That is a bit unusual. Did the OE knock sensors perform properly when removed?
Did you torque the new sensors to 15 ft-lbs? Did you check the resistance from the sensor wires to the PCM?

I haven't had much success with aftermarket knock sensors. Seems like they are prone to set codes, or just not work at all.
I just use GM knock sensors and have had good success with them.

Quote:

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Originally Posted by kevin87turbot

That is a bit unusual. Did the OE knock sensors perform properly when removed?
Did you torque the new sensors to 15 ft-lbs? Did you check the resistance from the sensor wires to the PCM?

I haven't had much success with aftermarket knock sensors. Seems like they are prone to set codes, or just not work at all.
I just use GM knock sensors and have had good success with them.

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Yes, with the original sensors installed before the engine was pulled, I never had an issue with the sensors, but I know they are prone to failure and the rear one was already pretty rusty so while I had it torn down I decided to replace them. I think at this point I will replace them with OE parts just to be sure. This still doesnt explain why it didnt throw a code with them completely disconnected and having gone through several drive cycles.

To answer all of you questions...yes they were torqued to the factory spec of 15flbs +-1 and the harness tested fine at 0.00ohms on auto range from the connector at the top of the manifold to the contact at the pcm with it unplugged and tested at 107kohm, I think, from the pcm connector to engine ground with the sensor connected.