Mitsubishi 3000GT 1991, Service Manual

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13-62
FUEL SYSTEM
On-vehicle Inspection of MPI Components
ENGINE COOLANT TEMPERATURE SENSOR
Coolant temperature
Coolant temperature
Coolant temperature sensor
Equipment side
connector
2
Engine control unit
OPERATION
l
The engine coolant temperature sensor converts the engine coolant temperature into a voltage and inputs
it to the engine control unit, which then controls the fuel injection rate and fast idle speed when the
engine is cold based on the input signal.
l
The 5 V power in the engine control unit is supplied via a resistor in the unit to the engine coolant
temperature sensor. Through the sensor which is a kind of resistor, it is grounded in the engine control
unit. The engine coolant temperature sensor resistor has such characteristic that its resistance decreases
as the coolant temperature rises.
l
The engine coolant temperature sensor terminal voltage increases or decreases as the sensor resistance
increases or decreases. Therefore, the engine coolant temperature sensor terminal voltage changes with
the coolant temperature, decreasing as the temperature rises.
TROUBLESHOOTING HINTS
If the fast idle speed is inadequate or the engine emits dark smoke during engine warm up operation, the
engine coolant temperature sensor is often faulty.
TSB Revision