Diagnostic Trouble Code (Dtc) P1112; Circuit Intermittent Low Voltage - Isuzu 1999 RODEO Workshop Manual

DIAGNOSTIC TROUBLE CODE (DTC) P1112 INTAKE AIR TEMPERATURE (IAT)
SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE
Circuit Description
The intake air temperature (IAT) sensor is a thermistor
which measures the temperature of the air entering the
engine. The powertrain control module (PCM) applies 5
volts through a pull–up resistor to the IAT sensor. When
the intake air is cold, the sensor resistance is high and the
PCM will monitor a high signal voltage on the IAT signal
circuit. If the intake air is warm, the sensor resistance
becomes lower, causing the PCM to monitor a lower
voltage. Diagnostic Trouble Code P1112 will set when the
PCM intermittently detects an excessively low signal
voltage on the intake air temperature sensor signal
circuit. DTC P1112 is a type D code.
Conditions for Setting the DTC
f The engine has been running for over 2 minutes.
f Vehicle speed is greater than 48 km/h (30 mph).
f IAT signal voltage is greater than 148°C (298°F)
(about 0.10 volt) for a total of 2.5 seconds over a
25–second period of time.
Action Taken When the DTC Sets
f The PCM will not illuminate the malfunction indicator
lamp (MIL).
f The PCM will store conditions which were present
when the Diagnostic Trouble Code set as Failure
RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
Records data only. This information will not be stored
as Freeze Frame data.
f The PCM will substitute a default value for intake air
temperature.
Conditions for Clearing the DTC
f A history Diagnostic Trouble Code P1112 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.
f Diagnostic Trouble Code P1112 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 IAT display on the Tech 2 while moving
connectors and wiring harnesses related to the IAT
sensor. A change in the IAT display will indicate the
location of the fault.
Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the Diagnostic Trouble Code to
6E1–309
D06RX043