First thing is to inspect the sensor visually and confirm it is intact. Then remove it, clean it and the block, and reattach it with the correct torque specs (which varies depending on which style of sensor--see the FAQ!). Make sure the connector contacts are clean and tight. Testing the wiring correctly requires checking values at the ignition computer, which is a PITA. But with the ignition off you can at least use an ohmmeter to check to make sure pin 2 in the connector is properly grounded (zero resistance between the connector and a good ground, like the ground wires attached to the nearby fuel rail).

I went thru Knock sensor hell on my 940 until I rerouted the wiring to eliminate induced currents. That is a design fault afflicting some 940's, nobody has experienced that on the 240's.

john
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1989 245 245K / 1993 945 131K