P0117 Ect Sensor Circuit Low Voltage - Isuzu 2000 Trooper Workshop Manual

Diagnostic Trouble Code (DTC) P0117 ECT Sensor Circuit Low Voltage
Circuit Description
The engine coolant temperature (ECT) sensor is a
thermistor mounted on a coolant crossover pipe at the
front of the engine. 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.
Conditions for Setting the DTC
D Engine running time is longer than one minute.
D The ECT sensor signal indicates an engine coolant
temperature greater than 150°C (302°F) (about 0.10
V) for a total of 50 seconds over a 100–second period.
Action Taken When the DTC Sets
D The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.
D 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.
D The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Conditions for Clearing the MIL/DTC
D 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.
D A history DTC P0117 will clear after 40 consecutive
warm-up cycles have occurred without a fault.
D DTC P0117 can be cleared by using the Tech 2 "Clear
Info" function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
D 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.
D Damaged harness – Inspect the wiring harness for
damage. 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 DTC P0117 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.
If it is determined that the DTC occurs intermittently,
performing the DTC P1114 Diagnostic Chart may isolate
the cause of the fault.
6E–157
D06RY00169