Toyota MR2 Supercharger

4A-GZE Knock Sensor

The Toyota 4A-GZE engine is fitted with a knock sensor, however there is little information about the device available, even from the Toyota's workshop manual. This page should fill in some of the blanks if your after some more information about it.

The knock sensor is a piezoelectric device that listens to the engine, the ECU monitors the 'noise' listening for the telltale signs of knock and responds by altering the engine timing.

The knock sensor fitted to the GZE engine is a single wire device earthed through the block, it's attached to the 4A block under the intake manifold on the left hand side.

Not being able to find any useful information about testing a knock sensor i hooked a spare upto a Velleman HPS10 handheld scope.

Settings: Horiz: 0.1ms / division, Vert: 1.0v / division

Using a metal object tap the sensor on it's nose, the image below shows a typical output. Frequency showing is around 11khz. In the future i hope to capture some real outputs on a running engine.

As you can see, it's a sine wave output with 6.4volts peak-to-peak, of course this changes depending how hard you tap it and what you tap it with.


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