30
    LAUNCH
 X-431 PADII
 
User's Manual
from the left.
[
]: Reduces the range and zoom in the waveform.
[
]: Increase the range and zoom out the waveform.
[
]: Starts or stops the testing process.
6.4.2 Test sample
Knock sensor testing
(1) Resistance test for knock sensor
Switch ignition “OFF”, unplug the wire connector of knock sensor, test 
the resistance between the wire terminal and the case of knock sensor 
with  “Resistance test” function,  it  shall be  ∞  (disconnected), and if  it 
is 0Ω(conductive),  which means the knock  sensor shall be replaced. 
For the magnetostriction knock sensor, it can also test the resistance 
by the “Resistance measurement”  function;  the  resistance shall be 
compliant with the specied value (see specic service manual for the 
detailed data), otherwise, the knock sensor shall be replaced.
(2) Checking for the output signal of knock sensor
Unplug the  wire connector of knock sensor, check  voltage between 
knock sensor connector terminal and ground wire of knock, it should 
be  output  pulse  voltage;  otherwise,  the  knock  sensor  shall  be 
replaced.
Coolant temperature sensor testing
(1) Resistance test for coolant temperature sensor
On vehicle testing:
Switch  ignition  “OFF”  and  unplug  the  wire  connector  of  coolant 
temperature  sensor, then use the “Resistance measurement”  to  test 
the  Resistance  between  two terminals  of  sensor. The  relationship 
between the resistance and the temperature is in inversely proportion 
(negative temperature coefcient), which shall be less than 1kΩ during 
warming up.
Independent testing:
Unplug the wire connector of coolant temperature sensor, then remove 
the sensor from the engine; place the sensor into a breaker with water 
and heat the water, then use the “Resistance  measurement”  to test 
the Resistance between two  terminals of coolant temperature sensor 
at different water temperature. Compared the measured value with the 
standard value, if the Resistance  is  not compliant with the standard, 
then the coolant temperature sensor shall be replaced. 
(2) Output signal voltage testing for coolant temperature sensor
After installing the coolant temperature sensor, plug the wire connector 
of sensor, and then  switch  ignition  ON, test the output signal voltage 
between the two terminals of wire connector. The tested voltage shall 
be  in inverse  proportional with the coolant temperature.  When  the 
harness of coolant temperature  sensor  is disconnected, the voltage 
shall be about 5V if the ignition switch is ON.