Engine stumble when hit and knock sensor codes

[Jessnco]

04 Yukon 5.3 flex. When I got this vehicle in Sept. last year they told me the cats needed replaced. I drove it home and anytime I pressed the accelerator pedal to the floor it would stumble and fall flat. Checked codes and it said knock sensors and fuel pressure regulator were bad. Nothing about cats. Changed knock sensors and regulator. Has ran great until recently. This time it through a code for cat bank two, MAF sensor. Replaced both cats and MAF sensor. Now it shows knock sensor codes again and is falling flat on its face again. Except it's different this time. It runs absolutely great until it gets hot. Temp gauge shows 198-210°F code reader shows the same temp and with a handheld temp reader different spots on radiator and motor runs between 175 and 205°F so not overheating. Just curious as to why it runs awesome for about 45 minutes and then stumbles under acceleration. It won't kick down into passing gear due to stumble. Just falls flat. When KS were bad the first time it stumbled right away. I checked ohms through wire to sensor( did not remove intake) and both read the same 110.3-110.5. Pretty sure they are both good. Code is for bank 2 knock sensor. Bank 1 has no code. Do not want to take I take off if they are good. Can it be something else? Can I check ecu? If so how? Any help is appreciated. Already spent more than what it's worth but I love the vehicle. Mileage is 217827. Rebuilt at some point. 120-125 psi compression every cylinder. Can clear code and it comes back after it stumbles.

 

[Fless]

Would you post the specific codes that you're dealing with? I'm a bit doubtful that this model would have any codes for fuel pressure or a FPR, since there is no PID for that.

I would recommend a standard fuel pressure test. Has the fuel filter on the driver's side frame rail been replaced, ever?

 

[Jessnco]

Would you post the specific codes that you're dealing with? I'm a bit doubtful that this model would have any codes for fuel pressure or a FPR, since there is no PID for that.

I would recommend a standard fuel pressure test. Has the fuel filter on the driver's side frame rail been replaced, ever?

The only codes it's throwing are for knock sensor. When I first got it is when it had a fuel pressure regulator code and knock sensor codes. The sensors were bad at that time.
The current codes are p0332, p0327

 

[Fless]

What was the "FPR" code? These are vacuum FPRs and don't have an electronic connection to the ECM, nor is there a fuel pressure PID.

I would say that some specific diagnosis is needed. What brand were the knock sensors, and was the knock sensor harness changed?

 

[Jessnco]

What was the "FPR" code? These are vacuum FPRs and don't have an electronic connection to the ECM, nor is there a fuel pressure PID.

I would say that some specific diagnosis is needed. What brand were the knock sensors, and was the knock sensor harness changed?

I do not know what an fpr code is. Yes the harness was changed. I bought a kit that came with both sensors and harness. I believe it was a Dorman kit from Oreileys

 

[Jessnco]

What was the "FPR" code? These are vacuum FPRs and don't have an electronic connection to the ECM, nor is there a fuel pressure PID.

I would say that some specific diagnosis is needed. What brand were the knock sensors, and was the knock sensor harness changed?

If both sensors are reading the same ohms and I am only getting a code for one of them, would that indicate an even issue?

 

[Fless]

FPR = fuel pressure regulator

 

[Fless]

Here's a video that walks through some of the diag for those codes. You might find it informative.

 

[rdezs]

110k ohms is the upper level for testing good. Your numbers are higher than that so you're knock sensors are not within the parameters and need to be replaced. That is if you tested them each individually and not through the harness? If you tested them through the two wire plug into the harness, that wire will have some resistance as well and affect an accurate reading.

Pull the intake, remove the harness plug to the knock sensor and check the resistance of the sensor by itself. You may find your knock sensor harness has too much resistance in it and possibly that's all that needs replaced. Could also be a corroded connection at either end of that short harness.

FPR code refers to fuel pressure regulator code.

Not applicable in your situation, you have a non-electronic vacuum operated fuel pressure regulator on the driver side of your fuel rail.

 

[Fless]

110k ohms is the upper level for testing good. Your numbers are higher than that so you're knock sensors are not within the parameters and need to be replaced. That is if you tested them each individually and not through the harness? If you tested them through the two wire plug into the harness, that wire will have some resistance as well and affect an accurate reading.

Pull the intake, remove the harness plug to the knock sensor and check the resistance of the sensor by itself. You may find your knock sensor harness has too much resistance in it and possibly that's all that needs replaced. Could also be a corroded connection at either end of that short harness.

FPR code refers to fuel pressure regulator code.

Not applicable in your situation, you have a non-electronic vacuum operated fuel pressure regulator on the driver side of your fuel rail.

I have read in a few places that the resistance range is 93k to 107k ohms, but I don't have a primary source for that spec.