I have a 944S2 and want to know how to inspect the two knock sensors. They look a little corroded and I am suspect of them working to spec. I want to make sure my DME isn't defaulting to a safe-mode on the fuel setting.

 

Try hooking up a voltmeter to the line, then tap the block with a wrench. Not sure if you'd need to measure the resistance or the voltage. In any case, if its flatlined, at least that would tell you if it was shot.

 

A scope would be best. See if you can borrow one, or maybe you have one already!

 

Someone said that the engine should shudder a little if you tap on the head with a hammer while it idles. Haven't tested it myself. Just don't tap to hard...

 

Did that (using a rubber mallet and then used a screw driver) but nothing happened. But then, i was told that the sensors knew i was cheating.......whatever that meant.

 

If the sensor is working it will put out a signal even if the motor isnt knocking. The engine never stumbles at idle with this, the KLR only retards timing if knock sound happens under specific conditions. Maybe boost, and certain degrees of crank rotation, I am not sure. Check it with a scope at idle, if you see a signal, in all likelyhood you are fine.

 

besides the 2 knock sensors there is a hall effect sender attached to the cam's timing belt gear. if knock detection is not working the timing retards 6 degrees (defaults) and stays there. the right way to test that all is working is to use the 9268 diagnostic tester and follow the Work Shop Manual’s instructions.

<edit>this relates to the 16 valve

 

I replaced the Hall Sender back in August because the bosch connector was cracked. There is some slight corrosion on the bolts that hold the knock sensors. I was going to pull both sensors and clean them; reinstall and see if there is a difference in engine performance.