Gilera Nexus 500 Workshop Manual page 269

Nexus 500
1 electronic control unit
2 Valve position sensor
3 Air temperature sensor
4 Fluid temperature sensor
The coolant temperature sensor is installed on the engine head and provides the indications for the
digital instrument and for the injection.
It is realised with two electrically different sections.
The injection section is realised with an NTC sensor connected to a 5V powered circuit. The resistance
variation causes a variation of the circuit voltage. Such voltage is combined with a temperature value.
By this value, the control unit can manage the engine operation, optimising it for all temperatures.
A failure of this circuit causes the switching on of the injection indicator and the tripping of the safeties
(among which the electric fan continuous start). In these conditions, the engine works, even though not
in an optimum way, always safeguarding the catalytic converter integrity.
A false temperature value that falls within the range of possible temperatures is a failure very difficult
to manage. This can cause a failure of the safeties and an improper management of the ignition. Such
failure is more easily detected upon the engine start-up.
To check the sensor and related circuit, proceed as follows:
1 - Connect the injection diagnostic tester and select the menu on the "errors" function.
Check whether faults have been recorded regarding the coolant temperature sensor.
YES go to 3 NO go to 2
Specific tooling
020460Y Scooter diagnosis and tester
2 - The EMS system has received no indications of temperatures out of the range of possible temper-
atures.
If you suspect a wrong temperature indication, proceed to perform the following check.
N.B.
A WRONG TEMPERATURE SIGNAL CAN BE DETECTED BY COUPLING THE ANALOGUE IN-
STRUMENT INDICATION WITH THE ELECTRIC FAN START.
IN ANY CASE, BEFORE CHECKING THE SENSOR, CHECK THE FILLING AND BLEEDING OF
THE COOLING SYSTEM
3 - Before checking the sensor and the relevant circuit, wait until the engine has cooled down and the
scooter has set to the working area temperature.
YES go to 4
4 - Set the switch to "ON" with switch to "RUN" and side stand raised. Select the menu on the "param-
eters" function. Do not start the engine.
YES go to 5
5 - Check the following values: coolant temperature sucked air temperature ambient temperature The
three indications are equal or they are slightly different (e.g. 1° C).
CIRCUIT LAYOUT
Specification
Injection
Desc./Quantity
INJEC - 77