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
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.