J30T Knock Sensor

10-28-2004, 07:27 PM
Hi to all,

I have a 1994 J30T ran ECU diagnostic and Iím getting Knock Sensor.

My question is if the knock sensor can be relocated and/or by passed same as in the 300ZX since they have the same engine.
I own a 1990 300ZX and I know how to do the fix in it, just need some instructions on how to do it on the J30T.

Any help will be greatly appreciated.


11-06-2004, 08:56 PM
Same thing for me.

I bought the stock engine knock sensor from the dealer ($200), a 300ZX non-turbo works for sure. I simply cut into the wiring harness and connected up my new knock sensor, and placed in the fender well. Although useless, it now runs great, just remember to always put supreme gas. To install it properly would be over 8hrs of work, and I didn't think it was worth it.

I've heard that you may be able to get away with just a resistor, saving you $200. The sensor sends Pulses on a voltage signal, so no pulses=no retard engine.

11-24-2004, 07:50 PM
Just for your information,the knock sensor is a piezoelectric device{microphone}.It listens for ping frequency then sends an audio signal to ECM.

12-08-2004, 06:59 AM
Hey you guys have good ideas: why bother replacing the KS...

Says like this: Knock Sensor (KS):
This is attached to the cylinder block and senses engine knocking through a piezoelectric element. A knock is transmitted as vibrational pressure through the sensor which is then converted into a voltage signal processed by the ECM


by Steve Zack - OTC Technical Trainer

As the piston rises during the compression stroke, the opposite force of compression in the upward direction and the downward force created as a result of preignition will cause the piston to rock, slapping the piston skirt against the cylinder wall, causing a knock.. When this happens the scanner should have an excessive coolant temperature reading. As a result of an engine knock, we should see the scanner knock reading indicate yes, with a command to retard ignition timing.

The firing line voltage will exceed 12 KV. With excessive preignition, the early flame front comes in contact with the spark ignition flame front. This will result in high HC, low CO, high 02, low C02, and high NOx. The horsepower of the engine will suffer as well.


Knock reasons:
- Ign timing too early [comparede to gas octane]
- spark plugs: Too high a heat range will cause pinging.
- probably have a carbon deposit buildup on your valves and in the combustion chamber - preignition


One piezo element from electronics shop must be under 2$ [As Nissan dealers always add two zeros...] and so they have almost similar (maybe even same) electrical characteristics as the original . Its very cheap to Test...

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