pyro719

Ok So I know you can disable the knock sensor in my car with a 3.9k resistor, wich I plan on doing. Well can I put another resistor on a switch so it will pull like 6 degrees of timing when the nitrous is armed?

Injuneer

No. The resistor is just put there to match the resistance of the knock sensor, so the PCM sees 2.5V on the circuit, and assumes the knock sensor is still there. The knock sensor's is a piezo microphone, and the output signal is a variable frequency representing the noise the microphone is picking up. That frequency is "riding" on the 2.5V circuit from the PCM. Changing the resistance doesn't provide a variable frequency.

pyro719

Oh ok. Guess I'll have to pull timing with a mallory 685.

JDL_Z28

Just out of curiosity, will the knock sensor be disabled if you just unplug it?

Injuneer

It obviously won't work if its not plugged in. But that sets a code (DTC 43) for the missing sensor, and the PCM runs almost constant retard (up to 15 degrees), based on engine operating parameters.