6E1–106
X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
DIAGNOSTIC TROUBLE CODE (DTC) P0118 ENGINE COOLANT
TEMPERATURE (ECT) SENSOR CIRCUIT HIGH INPUT
D06RX117
Circuit Description
The engine coolant temperature (ECT) sensor is a
thermistor mounted in the engine coolant stream. The
engine control module (ECM) applies a voltage (about 5
volts) through a pull–up resistor to the ECT signal circuit.
When the engine coolant is cold, the sensor (thermistor)
resistance is high, therefore the ECM will measure a high
signal voltage. As the engine coolant warms, the sensor
resistance becomes less, and the ECT signal voltage
measured at the ECM drops. With a fully warmed up
engine, the ECT signal voltage should measure about 1.5
to 2.0 volts. If the ECM detect a continuous open in the
ECT sensor or circuit, then a code P0118 will set. DTC
P0118 is a type A code.
Conditions for Setting the DTC
D
Engine running time is longer than 2.5 minutes.
D
The ECT sensor signal indicates an engine coolant
temperature of –39
°
C (–38
°
F) or less (about 5 volts)
for a total of 12.5 seconds over a 25–second period.
Action Taken When the DTC Sets
D
The ECM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.
D
The ECM will substitute the ECT reading with a default
engine coolant temperature value. The default value is
based on start–up intake air temperature and running
time.
D
The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
D
The ECM will turn the MIL OFF on the third consecutive
trip cycle during which the diagnostic has been run and
the fault condition is no longer present.
D
A history Diagnostic Trouble Code P0118 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.
D
Diagnostic Trouble Code P0118 can be cleared by
using the Scan Tool’s ”Clear Info” function.
Diagnostic Aids
Check for the following conditions:
D
Poor connection at ECM – Inspect harness connectors
for backed–out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal–to–wire connection.
D
Damaged harness – Inspect the wiring harness for
damage, shorts to ground, shorts to battery positive,
and open circuit. If the harness appears to be OK,
observe the ECT display on the Tech 2 while moving
connectors and wiring harnesses related to the ECT
sensor. A change in the ECT display will indicate the
location of the fault.
If Diagnostic Trouble Code P0118 cannot be duplicated,
the information included in the Failure Records data can
be useful in determining vehicle mileage since the