99 Lumina - Knock Sensor Code P0327

[fredsmythson]

I recently had the check engine light come on in my 99 Lumina 3.1L. The code scanner showed a code P0327, which is a knock sensor issue. After researching the code, the three possible causes are a defective knock sensor, faulty wiring or a bad PCM.

 

Is there a good way to test the knock sensor? Thanks...

[RobertISaar]

multimeter. IIRC, you should see about 100Kohms on it, much outside of that and it will cause problems.

[fredsmythson]

For the ohms test it showed 103k ohms on the knock sensor... I also did a voltage reference check on the PCM side - I unplugged the sensor connector and got a reading of 0.05 DCV from the PCM. Then I did a back probe test with the connector plugged in - also got a reading of 0.05 DCV.

 

After inspecting the knock sensor, I noticed the plastic connector on the knock sensor itself was loose and could be moved from side to side. I replaced the knock sensor and erased the codes. I drove the car and after eight miles the check engine light came back on again. I scanned the codes again and it came up with the same code of P0327.

 

So, I'm back to where I started from... I'm wondering if the reference voltage from the PCM is right. I think most cars have 5 volts going to the knock sensor. Would the next step be to do a continuity test between the knock sensor connector and the PCM? Thanks...

[RobertISaar]

with the sensor disconnected, you should see 5 volts. with it connected, roughly 2.5 volts.

 

what kind of meter are you using? if it doesn't have enough impedance, it will draw too much current from the circuit and make voltages appear lower than they are.

[fredsmythson]

For the voltage reference check from the PCM I was using an inexpensive Cen-Tech DMM from Harbor Freight Tools. I saw the reply here, and then upgraded to a more expensive DMM from Harbor Freight Tools (Cen-Tech 37772) which has 10 meg ohms of input impedance. I checked the reference voltage again from the PCM with the new DMM and it showed the same reading - 0.047 dcv.

 

I went ahead and replaced the knock sensor. The ohms test for the new knock sensor uninstalled was 99k ohms.

 

I also took out the PCM to check the connections. I checked the ohms reading at connector C1, pin 33. It showed 4.8K ohms. Check the continuity of the connection between the knock sensor and PCM. Checked the ohms reading from the knock sensor connector to the PCM - showed 4.8K ohms.

 

Does this indicate there might be a problem with the PCM? I'm still wondering why I'm getting 0.047 dcv from the PCM to the knock sensor connector. I had the DMM on the 20 volt DC setting.

[fredsmythson]

Thanks for everyone's help on this P0327 code issue...

 

I recently replaced the PCM computer with another PCM. This was a used PCM that I bought on Ebay that was updated with the latest software and the car's VIN. The car seemed to idle better with this replacement PCM, but the the check engine light came on after about two miles of driving. I checked the code, and yet again it was the same code that came up - P0327.

 

Here is an update on what I've done so far:

 

Replaced the knock sensor

Checked the wiring between the knock sensor and PCM (checked out good)

Replaced PCM

 

Just to check the replacement knock sensor, I kept the knock sensor connected to the PCM and disconnected it from the engine block. I then connected a jumper wire to the threaded part of the knock sensor and connected the other end to the battery ground. Drove the car and the check engine light came on after about eight miles - same code, P0327.

 

I'm not sure where to go from this point. I don't have any advanced scan tools to use and I'm having a hard time finding a scan tool that would help diagnose a P0327 code.

 

I read in the GM shop manual that a P0327 can set if there is an issue with the crankshaft positioning sensor. Any ideas on what to look at next? Thanks!

[fredsmythson]

After months of trying to solve this P0327 knock sensor code and replacing different parts, I finally found the problem.

 

It ended up being a crankshaft positioning sensor that was covered in oil and dirt. I installed a new crankshaft positioning sensor and now the check engine light is OFF. Also, the car's idle has greatly improved - no more variable idle. I'm happy to finally solve this problem...

[LumiLTZ]

Glad you found and fixed the problem.