Diagnostic Trouble Code (Dtc) P0117 Engine Coolant Temperature (Ect) Sensor Circuit Low Input - Isuzu 1999 RODEO Workshop Manual

6E1–126 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
DIAGNOSTIC TROUBLE CODE (DTC) P0117 ENGINE COOLANT TEMPERA-
Circuit Description
The engine coolant temperature (ECT) sensor is a
thermistor mounted in the engine coolant stream. The
powertrain control module (PCM) 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 PCM will
measure a high signal voltage. As the engine coolant
warms, the sensor resistance becomes lower, and the
ECT signal voltage measured at the PCM drops. With a
fully warmed–up engine, the ECT signal voltage should
measure about 1.5 to 2.0 volts. DTC P0117 is a Type A
Code.
Conditions for Setting the DTC
f Engine running time is longer than two minutes.
f The ECT sensor signal indicates an engine coolant
temperature greaterthan 150°C (302°F) (about 0.14
V) for a total of 12.5 seconds overa 25–second period.
Action Taken When the DTC Sets
f The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.
f The PCM 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.
TURE (ECT) SENSOR CIRCUIT LOW INPUT
f The PCM will store conditions which were present
when the Diagnostic Trouble Code was set as Freeze
Frame and in the Failure Records data.
Conditions for Clearing the MIL/DTC
f The PCM 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.
f A history Diagnostic Trouble Code P0117 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.
f Diagnostic Trouble Code P0117 can be cleared by
using the Scan Tool's "Clear Info" function.
Diagnostic Aids
Check for the following conditions:
f Poor connection at PCM – Inspect harness connectors
for backed–out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal–to–wire connection.
f Damaged harness – Inspect the wiring harness for
damage, shorts to ground, shorts to battery positive,
and open circuits. 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 P0117 cannot be duplicated,
the information included in the Failure Records data can
be useful in determining vehicle mileage since the
D06RX044