Knock Sensor Failure?

Closed/Open Loop have nothing to do with the knock sensor, this relates to the oxygen sensor thats in the exhaust. When you do a cold start the oxygen sensor is too cold for it to work, so the car runs off of the coolant sensor and a set of predetermined fuelling values, once the coolant reaches a certain temperature the hot gases exiting the engine will have warmed the oxygen sensor enough for it to start working, until now the engine has been running "open loop", but now the engine is warm enough it starts using the oxygen sensor for metering the fuelling, this is "closed loop".

The knock sensor is basically a type of microphone that sits on the block and listens for detonation, if it detects any the timing will be retarded to prevent further detonation and possible damage to the engine. I don't know the engine you've got but I'll make a guess that it runs a motronic system, here in the UK some cars about as old as yours have seen this fault code appear because of the wiring to the knock sensor, its normally a short cable that plugs into the main loom and the sensor.. not saying thats the problem but if a new sensor doesn't fix it try that cable. Beware on a V6 you may have 2 knock sensors ( one for each bank ) but Im not sure on that.

Good luck.

My suggestion too. Check the wires and the connectors BEFORE you replace the sensor. If you search the web you can find a test for the sensor. You tap the area near the sensor with a hammer to set it off. I think I saw the test on a turbo Buick site??

Al

You tap

Yep rapping a spanner on the block/inlet manifold should cause noise for the sensor to pick up...

Thanks for your help Mark, but maybe Harryface or someone who's replaced a knock sensor on a GM 3800 V6 before can better explain the Reason for failure.

I know what the sensor does, I even know where its located and how it operates in relation to the engine's PCM. Also as I have stated, the computer does NOT look at the data from certain sensors including the knock sensor UNTIL the system has reached proper operating temp. This may not be the case for all cars, but in my case it is.

Thanks in advance.

Shane W.

Knock sensors have a low failure rate because there just isn't much there to fail. If you suspect the knock sensor, check to make sure that the sensor wire isn't shorting out against the exhaust manifold. Sometimes the wire will make contact and the insulation will melt off, causing a short. BTW when replacing the sensor, drain the cooling system first (it'll be a much dryer job that way). Rich B

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% There are two classes of pedestrians in these days of reckless motor traffic - the quick and the dead. ~ Lord Dewar 1933 ~

Climbing into a hot car is like buckling on a pistol. It is the great equalizer. ~ Henry G. Felsen 1964 ~

Thanks very much for your suggestions.

The KS is piezo. Not much to go wrong except perhaps a wire falling off the crystal.