Knock sensor trouble shooting

[robthorp]

Looking for a little help.

 

I have a 2002 Silverado 2500 HD with a 6.0L and automatic, it's been trouble free for 13 years and 175K miles but now the following issue has developed and it's knocked about 10% off my MPG also.

 

I've been getting a P0332 trouble code and I would like to test as much as I can before tearing the intake off to replace the knock sensors and wiring harness. I tried the following tests and I'm wondering if there is something else to check before replacing parts.

 

1. Measured the AC voltage from each sensor while tapping on the block with a hammer. Both sensors put out 50 plus mV depending on which side of the block was struck. This was done with a DVM and not a scope so readings are very inaccurate, but both responded.

 

2. Switched the wires at the connector up on the drivers side of the intake. The result was the code switched from P0332 to P0327, which tells me the connection to the ECM is good since the problem followed the wire.

 

3. Measured the resistance to ground of each of the sensors. One was 102K and the other 103K, both in the range I believe.

 

I have read a lot of posts regarding this subject and I currently don't have a full scanner just a cheap little one to tell me the codes and allow me to reset them. I have ordered one that will show me the state of the ECM but haven't received it yet. Any suggestions or should I just assume that the sensor is bad and replace them both and the wiring harness?

 

Thanks for your help.

 

Rob

 

[davester]

I would say do it. Change both sensors + the harness that connects to them [it's short, just goes from the sensors to just out the back of the engine, and then there is a plug that connects to the main harness], and then intake manifold gaskets.

 

Also check that all your exhaust bolts are intact, as they tend to break in these motors and air leaking into the exhaust also makes your engine glup down the gas [as it throws off the O2 sensor, which throws off the engine computers settings. You may want to consider replacing these bolts semi-regularly [every year or two]...