2005 GMC Sierra 1500 P0332 - specific knock sensor questions inside

[jmpidgeo]

Hello all,

 

Recently (couple weeks ago) I replaced both knock sensors when my MIL came on and threw code P0332 (knock sensor bank 2 low voltage input IIRC). I knew that only one sensor was affected by the code but I replaced both just because. I did however notice that the bank 2 sensor connection was easier to come off than bank 1, which I think may come into play later on in this story. Of course, both knock sensors were submerged in water, which I cleaned out. I did NOT do the silicon-dam method, as I discovered this after I was done with the job. I did not replace the wiring harness either.

 

The MIL was off for at least a week before it came back, P0332 again.

 

Yesterday I did some diagnosis to try and figure out what is going on with this.

 

Bank 1 and bank 2 sensor (ohmed out at the harness plug on intake) both show a resistance of 99-100 kOhm (or Ohm, can't remember) with the engine off.

 

I then checked the response of each sensor.

 

Bank 1 and bank 2 sensors both showed a change in voltage when tapping on the block with a hammer, which is good.

 

I then started the engine up and measured the voltage change with RPM change for each sensor, and here is where it gets interesting

 

Bank 1 sensor fluctuated from approximately 50 mV to 150 mV with a quick RPM sweep (friend stabbed the gas pedal quick to change the sensor output)

 

Using the same technique, Bank 2 sensor fluctuated from approximately 50 mV to 100 mV, which was significantly different than the bank 1 sensor.

 

Bank 1 and bank 2 pins from the connection on the intake manifold to the PCM show very similar resitances between them, signifying that there should be no short between the PCM and knock sensors themselves (unless the sensor harness is bad)

 

That completes all of the diagnostic trouble-tree steps I have taken via AllData. The next steps are PCM replacement, which I do not want to do.

 

I realize that the sensors may be designed to pick up specific frequencies and as such, different responses under the same conditons, but the sensors have the same P/N if I am not mistaken, so that must be the characteristics of the mounting location, right?

 

The fact that the bank 2 sensor electrical connection seemed to be loose compared to bank 1 has me wondering about the sensor wiring harness and the fact that the connection may be poor/intermittent. I am going to order one and replace it because it's a relatively quick and inexpensive job to do, but I was wondering if there is anything else that would make sense?

 

Thanks in advance!

[txab]

Replace the harness.

 

Did you properly torque the replacement sensors to 15 lb ft?

[jmpidgeo]

Replace the harness.

 

Did you properly torque the replacement sensors to 15 lb ft?

I did not torque them with a torque wrench. Went with my calibrated arm lol. When I replace the harness I'll torque them properly as well as the intake manifold bolts.

[Doug_Scott]

Took me a bit to figure out that "MIL" was just another way of saying "CEL". Was the entire sensor and harness connection under water? You can see by the voltage readings you got that we are not talking about a lot of voltage here. Any corrosion, or looseness on the connection can cause issues. I have never seen the location of the sensors, but, is the harness long enough to be able to swap the connectors? By this I mean can you take unplug the right sensor and connect that connector to the left sensor and vice versa? Reason for asking is if you can, you can test to see if the trouble code also moves to the other side. If it does, that points to the that part of the harness, making it easier to trouble shoot. Bad connection would be my guess.

I am being picky here, but this is one of my pet peeves... issues with wiring are not "shorts" normally. They are far more often an "open" issue. Shorts tend to be very easy to locate, opens are not easy. Shorts blow fuses, cause fires. Opens rarely blow fuses, and are even more less likely to cause a fire.

[Chris]

Just do the sensors and harness, They will eventually go bad. There is a TSB on this and the sensors are right under the intake manifold

 

 

[jmpidgeo]

I have the harness on order. I will be replacing that when I get it. There's no easy way to swap connections without doing all the work to replace the sensors anyways, so I'll just go ahead with the new harness. Both sensors were submerged when I replaced them before, but the rear sensor was worse off. I do believe that water had reached the connection.

[jmpidgeo]

Oh, MIL = malfunction indicator lamp, aka the general CEL term used by OEM's since sometimes it's a CEL or SES light. MIL gets rid of the cross-brand confusion

[Chris]

Rear is the one that goes bad. Dont forget go 0ick up some black RTV to seal them up. Look at mine

 

Sent from my Samsung GS4 using Xparent Red Tapatalk 2

 

 

[jmpidgeo]

Yup, I definitely plan on sealing them up this time

[jmpidgeo]

So I replaced the wiring last night. The code came back instantly. I loosened and retorqued the knock sensors and everything like that. My next step is to try a higher quality of knock sensor. If that does not work. Then it is onto the wiring connector at the manifold, where I would get a new one and install it with new pins. And if that doesn't work, then I will pay the $100 for my friend with HP tuners to deactivate the code.

[jmpidgeo]

Swapped sensors around. I am getting good at the repair procedure.

 

Bank 2 sensor was rusted worse on the sensor body than the original one I replaced.

 

So if the problem migrates to the bank 1 sensor I will know where my problem is. If not then its back to the drawing board.

[jmpidgeo]

Issue migrated to sensor 1 after swapping them. Sensor 2, when i removed it, was rusted worse than the original it replaced. Ordered AC Delco sensors and will be doing the silicon dam with them this time.

[jmpidgeo]

So far so good

[b1gted]

So far so good

 

Awesome. Looks like you got to the bottom of the issue.

 

 

- Sent from my sexy iPhone.

[jmpidgeo]

It was amazing how rusty the sensor was this time. 4 days from brand new looking to almost fully covered in rust. I hope I got that issue solved. I couldn't ever have imagined or believed that it could have happened that fast.