Where is the knock sensor
Knock Sensor Operation
the knock sensor is basically a
microphone connected to the engine block
the knock sensor is also tuned to the
very specific frequency of an engine
pinging inside the knock sensor is a
crystal and supporting contacts knock
sensors may have one or two terminals
with only one terminal the sensor is
grounded at the body itself with two
terminals one is ground and the other is
the signal wire itself the ACM expects
to see a normal signal output with a
normally running engine if no output is
seen then the ECM issues Nov d2 code P 0
3 2 4 through P 0 3 3 4 so a totally
quiet knock sensor equals a dead or
defective sensor but instead if the ECM
sees the normally operating signal it
then looks for pinging waveform
signature and when it does finds it
tries to adjust ignition timing
accordingly the timing adjustment is
done until the pinging stops if it does
then the ECM assumes a mechanical fault
with the engine on some older systems a
faulty knock sensor may set erroneous
OVD 2 codes for engine mechanical
problems when in fact it is the knock
sensor finally whenever faced with a
knock sensor OVD 2 code makes sure the
sensor wire is not broken disconnect and
perform a continuity test between the
sensor and the ECM sensor pin a sensor
range or performance code means that the
ECM has not detected the normally
running engine signal a circuit hike
means that only the bias diagnostic
voltage output by the ECM is seen or a
possible broken wire a circuit low means
that the sensor is shorted to ground
some newer vehicles may have to knock
sensors to better detect opening engine
the best way to test a knock sensor is
with the ADP scope one which will show
you the signal itself
![What Is A Knock Sensor? (Detonation, Pinging) [FREE LESSON]](https://img.youtube.com/vi/VVW_Ghda_tM/mqdefault.jpg)
