1F–74 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F110
DIAGNOSTIC TROUBLE CODE (DTC) – P0118 ENGINE COOLANT
TEMPERATURE SENSOR HIGH VOLTAGE
Circuit Description
The coolant temperature sensor (ECT) uses a thermis-
tor to control the signal voltage to the engine control
module (ECM).
The ECM supplies a voltage on the signal circuit to the
sensor. When the air is cold, the resistance is high;
therefore the ECT sensor signal voltage will be high.
As the engine warms, the sensor resistance becomes
less, and the voltage drops. At normal engine operating
temperature, the voltage will be between 1.5 and 2.0
volts at the ECT sensor signal terminal.
The ECT sensor is used to the following items:
D Fuel delivery.
D Lock Up Clutch (LUC).
D Ignition.
D Evaporator Emission (EVAP) Canister Purge Valve.
D Idle Air Control (IAC) valve.
D Electric cooling fan.
Conditions for Setting the DTC
D This DTC can be stored in “key-on” status.
D The engine rum time is greater than 3 seconds.
D The ECT sensor indicates that the engine coolant
temperature is less than –40°C(–40°F).
D ECT voltage is greater than 4.98V.
D A low voltage condition exits.
Action Taken when the DTC Sets
D The Malfunction Indicator Lamp (MIL) will illuminate.
D The ECM will record operating conditions at the time
the diagnostic fails. This information will be stored in
the Freeze Frame and Failure Records buffers.
D A history DTC is stored.
D The coolant fan turns ON.
D The ECM will substitutes a fixed MAP value and use
TP to control the fuel delivery (the scan tool will not
show defaulted)
Conditions for Clearing the MIL/DTC
D The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
D A history DTC will clear after 40 consecutive warm-up
cycles without a fault.
D DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
After the engine has started, the ECT should rise steadi-
ly to about 90°C(194°F) then stabilize when the thermo-
stat opens.
Use the temperature vs. resistance values table to eval-
uate the possibility of a skewed sensor. Refer to “Tem-
perature vs. Resistance” in this Section.
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