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Shown here before the protective coating has been applied
Shown here before the protective coating has been applied

Knock Sensor Bypass Plug



This Knock Sensor Bypass Plug connects directly to the EFI Harness where the Knock Sensor Sub Harness would normally connect near the back center of the intake manifold. 

This can be used to clear a Code 34 to verify the knock sensor circuit is working properly and the issue lies with the sub-harness or knock sensor itself.  This is not recommended to be used to permentately eliminate the knock sensor as the knock detection system is an important part of the 300zx's Electronic Control Unit.  

A diagnostic trouble code 34 generated by the ECU means that the circuit for the detonation sensor is broken, not that the ECU has "heard" detonation.  The ECU is always looking for a resistance in the detonation sensor circuit of around 1 mega-ohm.  If this resistance is not present the ECU throws a code 34 and also goes into a self protection mode in which ECU switches to more conservative safety maps with less timing and more fuel as well as lowers the boost level on Twin Turbo models by opening solenoids that normally bleed off some of the pressure to the wastegate actuators.  The faulty part in the detonation sensor circuit is usually the sub-harness between the sensor itself and the EFI harness.  Corrosion on the terminals of the connector between the sub-harness and the detonation sensor is usually the cause of a code 34.  Z1 sells the detonation sensor sub-harness HERE.  Now that Z32s are surpassing 20 years old, this system that was designed to help protect your engine from damage from things like low grade fuel often fails and results in poor performance and fuel economy even though there is no detonation taking place. 

The detonation sensor is located on top of the cylinder block in the valley between the heads under the intake manifold.  It is difficult to change or even clean the connections on unless you have your engine apart. Using this Bypass Plug, it is possible to eliminate a code 34 by tricking the ECU into believing the circuit is OK.  This Plug consists of a 1 mega-ohm resistor which crosses the two terminals that attach the detonation sensor sub-harness to the main engine EFI wiring harness.  This will eliminate the Code 34 allowing your ECU to function as normal, but will eliminate the self protection function of the detonation sensor altogether.  Nissan included the detonation sensor for a reason, so it's not recommended to eliminate it unless you are clear on how to minimize the risks. 


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