Launch X-431 User Manual page 91

LAUNCH Station
User's Guide
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 specified value (see specific 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 coefficient), 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.
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