I would sugest that the Ignition timing is locked in retard....

Insert joke about other members here ==>

 

Strantor - did you ever resolve this? I have same truck, same problem, and same thought process. I replaced the knock sesnors with non-OEM, and problem didn't go away. I didn't quite make to applying a scope, however. While doing more research found this thread... I'm hoping you solved it?

Thanks

 

Strantor - did you ever resolve this? I have same truck, same problem, and same thought process. I replaced the knock sesnors with non-OEM, and problem didn't go away. I didn't quite make to applying a scope, however. While doing more research found this thread... I'm hoping you solved it?

Thanks

Tagging a person like this ==> @strantor is more likely to get his attention.

 

A company called Picoscope specialize in ICE faultfinding scopes and accessories. Don't know the costs involved, but if you can get access to someone who has one and knows how to use it I'm sure they will find the problem. Check them out on the net. They have lots of detailed tales of problem fixes.

 

have a look at this. May give some clues.
https://www.picoauto.com/library/case-studies/troubleshooting-a-v8-knock-sensor

 

I have a repairs manual here for a totally different car, but the steps might help:

Description
The two pins connected to the knock sensor (KS) are
separately signal output (KS end pin 1 connected to
ECU end pin 19), and signal output (KS end pin 2
connected to ECU Pin 20).
The knock sensor is mounted on the engine block, and
vibrates at different vibration frequencies under the
different engine operating conditions, and produces the
voltage signal containing different kinds of
frequency.This signal is magnified, filtered, rectified and
integrated in ECU, and in the end this integral value of
knocking signal is compared with the knock reference
value. And if the specific value exceeds a certain valve
value, a knock may be considered to happen, and the
ECU may retard the ignition timing based on it.
Diagnostic module may monitor the standardized knock
reference value (Unit: V).When the engine operates
normally, and the knock sensor is operative regularly,
the voltage signal of knock sensor may fluctuate in the
upper and lower limits corresponding to the RPM. Once
the signal voltage exceeds the valve value, the knock
sensor with trouble may be considered.Then the
following can be diagnosed:
－ Max. Failure: The background noise may
rise abruptly due to the engine damage.
－ Min. Failure: The background noise may be
extremely low due to a short or open circuit
to the ground.

Diagnostic Aids
Check the following:
* A poor connection with ECU - inspect the knock
sensor and the ECU connector.
－ Backed-out terminals
－ Broken locks
－ Improperly formed or damaged terminals

* Harness laying error - inspect the knock sensor
harness to ensure the harness is not too near to
the high voltage wire.
View the vehicle driving mileage since the last
diagnostic test failed in the trouble record, and
determine the frequency of occurrence in setting the
DTC. It is helpful to the diagnosis of the conditions.

 

Strantor - did you ever resolve this? I have same truck, same problem, and same thought process. I replaced the knock sesnors with non-OEM, and problem didn't go away. I didn't quite make to applying a scope, however. While doing more research found this thread... I'm hoping you solved it?

Thanks

Yes I eventually solved it a few months later. I should have come back and posted an update; shame on me. I went to the dealership and bought the OEM knock sensors, brought them home and installed them with a torque wrench to the specified value.

What I learned is that the OEM knock sensors for a 2005 GMC Sierra 5.3L are designed for a 2005 GMC Sierra 5.3L. The generic sensors at autozone a designed to be generic ("fit" as many kinds of vehicles as possible). Just because they FIT doesn't mean they output a signal with the exact amplitude that the 2005 GMC Sierra is looking for. Also, over/under torqueing them affects their output.

Taking the intake off sucks. I suggest you don't do it 3 more times like I did. Just once more. Go get the proper parts and install them properly. Don't forget to do the silicone dam to keep water out. Google it if you don't know what I'm talking about.

 

@strantor I bought a MAP sensor from Autozone that failed in a day. Oddly, the engine RPM was really low and would not stay running without the foot on the accelerator. When I disconnected the sensor, the car would at least run, so a tow was not required.

I suspect the "silicone dam" is a "trick" probably spelled out in the service manual. I replaced a mechanical fuel pump "on the side of the road" and I had a really hard time. You put grease on the actuator rod to keep it from falling out.

In another vehicle, I had an anti-freeze leak which I thought was a manifold gasket. I took the manifold off and found a 1" piece of hose with a slit in it.

 

I am unfamiiliar with the sensors on your engine , but very familiar with GM (& other) knock sensors on European and Japanese engines.
In all cases, that I know of, they need to be torqued. The 100kΩ "resistor" is actually a piezo sensor which must be precisely preloaded to work properly. Thus you will need to preload the sensor,to the correct torque.
There are two variations , one a solid sensor with a screwthread that screws into the block. The second type has a hole in the middle, in this case I would advise fitting a new bolt as well as the bolts often stretch in service..
It is important that the face of the block where the sensor sits is thoroughly clean and straight as any bit of dirt or rust caught between the sensor and the engine block will damp the signal and set a fault code.

 

@strantor I'm having the same problem with my knock sensors on a 2001 Chevy Suburban 2500 6.0L vehicle. I bought non-OEM replacement knock sensors and a wiring kit online, took the time to swap the sensors/wiring out and still getting the codes. My automotive guru buddy says to drive it a while and see what happens (cheap option to see). So far it's only been 2 days but keeps throwing the codes after I clear them (attached).

I get the proper resistance on the old sensors and new ones, around 100k each. I'm wondering your thoughts after having gone through this ordeal?? Get OEM sensors and replace the new ones that didn't work? Wait? Other ideas?

I don't have a torque wrench, but could borrow or buy one. Looks like Autozone loans them which I didn't think of when I was happily installing the new ones after cleaning the area out from the old.

How/Where did you learn this:

"5.3L are designed for a 2005 GMC Sierra 5.3L. The generic sensors at autozone a designed to be generic ("fit" as many kinds of vehicles as possible). Just because they FIT doesn't mean they output a signal with the exact amplitude that the 2005 GMC Sierra is looking for. Also, over/under torqueing them affects their output."​

Thanks!

 

@strantor I'm having the same problem with my knock sensors on a 2001 Chevy Suburban 2500 6.0L vehicle. I bought non-OEM replacement knock sensors and a wiring kit online, took the time to swap the sensors/wiring out and still getting the codes. My automotive guru buddy says to drive it a while and see what happens (cheap option to see). So far it's only been 2 days but keeps throwing the codes after I clear them (attached).

I get the proper resistance on the old sensors and new ones, around 100k each. I'm wondering your thoughts after having gone through this ordeal?? Get OEM sensors and replace the new ones that didn't work? Wait? Other ideas?

I don't have a torque wrench, but could borrow or buy one. Looks like Autozone loans them which I didn't think of when I was happily installing the new ones after cleaning the area out from the old.

How/Where did you learn this:

"5.3L are designed for a 2005 GMC Sierra 5.3L. The generic sensors at autozone a designed to be generic ("fit" as many kinds of vehicles as possible). Just because they FIT doesn't mean they output a signal with the exact amplitude that the 2005 GMC Sierra is looking for. Also, over/under torqueing them affects their output."​

Thanks!

My advice would be to get the OEM parts from the dealership and install them with a torque wrench. I learned the quoted section from scouring gearhead forums and from doing pseudoscientific experiments involving a vise, a hammer, an oscilloscope, and multiple knock sensors.