2002 Yukon/Another knock sensor thread

[pharpe]

I've been reading knock sensor posts and watching videos for 3 days and I'm really in need of some direction. I have a 2002 Yukon with a 5.3. It was throwing a knock sensor code. It was only one but I don't remember which. I watched some videos and ordered two new sensors and a new harness on Rock Auto (not AC Delco but good reviews). I did the swap and it all went well. Cleared the codes and let the truck idle about 15 minutes. No codes. I then drove about 30 miles and parked it. About 2 hours later I got back in and started driving. After 5 miles I got P0327 Current fault and P0332 Pending Fault. So I've been doing more research. It sees a lot of people recommend getting OEM sensors. So I went to my local Chevy dealer and bought 2 ACDelco sensors and a new AC delco wiring harness. I really don't like just throwing parts at this and I really really don't want to pull it all apart again just to have the same issue so I looked up how to test the KS.

I found this video

So I decided to test my original sensors vs the new ACDelco ones I bought. Resistance on the new ACDelco ones were right at 99 ohms. The original ones were about 108 but jumped around. Ok I guess that makes sense. Then I did the hammer tap voltage test. The original sensors registered 0.02-0.05 V. That seems low but both were reading something. Finally I did the hammer test with the new ACDelco and got nothing. I tried over and over with both new sensors and get no voltage at all. Could both be bad right from the dealer?

Now I don't know what to do.
Pull it apart and try the new ACDelco stuff and hope for the best?
Take these back and try another dealer and see if those pass the bench test?
I've seen people talking about putting in a resistor to test and see if there is an issue on the ECU side. Should I try that route?
I could try hooking up the new ones outside of the intake (would have to ground them) and see if I get the codes back. Not sure if this would work
Test me RockAuto non ACDelco sensors just to see what they say.

Would appreciate any help.

 

[Miami-Dade]

Welcome from Miami&NYC!

Moved you here.

 

[pharpe]

I tested the two knock sensors I already installed through the wiring. They both read about ~100 ohms steady so that tells me that the grounds and the wiring is good to the KS. I guess they could still be bad but it's really hard for me to believe that both brand new sensors are bad. I cleared the codes and let the truck run for about 30 minutes in the driveway. No codes yet. This knock sensor stuff is maddening.

Update: Ugh. After letting it run for 30 minutes in the driveway I took it for a drive. I did some hard exceleration and both KS codes came back as pending.

 

[rockola1971]

How do you know they arent telling you the truth and you have knocks? How old are plugs and wires?

 

[pharpe]

How do you know they arent telling you the truth and you have knocks? How old are plugs and wires?

From what I understand, if there are knocks, then the KS sense them and tell the ECU to pull out timing. They throw the low voltage codes if they are malfunctioning. Maybe I'm miss informed though.



Not sure of the age of the plugs and wires.

 

[pharpe]

So I pulled it all back apart and replaced both knock sensors and all the wiring with the ACDelco stuff. JCleard codes then did a drive and both P0327 and P0332 are back Pending Faults. No Idea what to do now.

 

[mattbta]

Sounds like you have a broken wire between PCM and harness. Ivan shows how he tests this:

 

[pharpe]

I tested resistance back to both KS and they are both 108. Then I tested voltage on the ECU side. Both tested consistent 28 mv

 

[rockola1971]

I tested resistance back to both KS and they are both 108. Then I tested voltage on the ECU side. Both tested consistent 28 mv

So both codes in initial post are bank 1 & 2 sensors. New harness so that eliminates that one. What else is common to both? The engine (knocking) and the PCM. Id check for active knock counts on engine running and maybe even under load. As far as the PCM id would pull connectors and inspect for the green crusty corrosion (water intrusion) and clean the hell out of it if it is there. Otherwise you may have a bad PCM or need a reflash of the program.

 

[Moosemoon]

Here’s what I think I learned with the knock sensor saga over the last several months on my 2001.
AC Delco are the best choice in KS parts.
But read somewhere that 50% of those are faulty out of the box.
Be sure to dam the sensors after installing to prevent moisture infiltration. There is a TSB on this.
Idling does not complete the drive cycle so that’s why the codes show up later after a roadtrip.
Replacing O2 sensors may or may not help. Didn’t for mine.
What finally seems to have fixed mine after the third go round of KS was replacing the Mass Air Flow Sensor.
Since that was done no KS codes and not pending either.
Yukon runs much better but still chasing other gremlins.