How do i bypass a 1997 Honda civic knock sensor?

Answer 1

Man, it feels so good getting rid of that CEL. Now I can pass smog!

So if anyone ever needs to bypass their knock sensor without tripping a CEL, here is what you need to know.

First of all, you can't ground it out or replace it with a resistor. The knock sensor is not an electrical load, it actually produces it's own voltage. Your ECU is looking for a variable voltage from the sensor.

So what you want to do is mimic the voltage output. Here is a guide of what to do:

1. First, go to Radioshack and buy a piezo transducer, part #273-073. You will find it will all the buzzers because that it's intended for. It costs $1.99.

2. Flip to the back of your haynes and look at the chassis electrical pages. Find which wire going into your ECU is for the knock sensor. If you have a 96-00 civic, it is the Red wire with a blue stripe. MAKE SURE YOU DON'T MISTAKE IT FOR THE BLUE WIRE WITH A RED STRIPE. That's for your AC system. Cut the wire about 6" from the ECU.

3. Tape the transducer to your fuel rail.

3. Weave a single wire from your fuel rail back to your ECU.

4. Connect the speaker wire to the (+) wire on the transducer.

5. Connect the other end of the wire to the Red/blue wire on your ECU.

6. Connect the (-) wire on the transducer to a good ground.


So basically, the positive wire of the transducer goes to the ECU and the negative wire goes to ground. I taped the transducer to the fuel rail because that's where I found it made the most voltage (most vibration).

The transducer only makes about a half a volt at 4k rpms and the ECU usually sees about 1.5 volts. So if you try this and it doesn't work, you will have to find a better location to tape the transducer or you will have to add a second transducer to bump up the voltage.