Isuzu Rodeo UE. Manual — part 403
6E2–367
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1112 IAT Sensor Circuit Intermittent Low
Voltage
D06RW078
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. DTC P1112 will set when the PCM intermittently
detects an excessively low signal voltage on the intake air
temperature sensor signal circuit.
Conditions for Setting the DTC
f
The engine has been running for over 2 minutes.
f
Vehicle speed is greater than 30 mph (48 km/h).
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 DTC was set as Failure 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 MIL/DTC
f
A history DTC P1112 will clear after 40 consecutive
warm-up cycles have occurred without a fault.
f
DTC P1112 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:
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. 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 DTC to be set occurs. This
may assist in diagnosing the condition.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
6E2–368
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
2. Verifies that the fault is present.
3. If DTC P1112 can be repeated only by duplicating
the Failure Records conditions, refer to the
“Temperature vs. Resistance Value Chart.” The
chart may be used to test the IAT sensor at various
temperatures to evaluate the possibility of a
“shifted” sensor that may be shorted above or below
a certain temperature. If this is the case, replace
the IAT sensor.
Intake Air Temperature Sensor
°
C
°
F
OHMS
Temperature vs. Resistance Values (approximate)
100
212
177
80
176
332
60
140
667
45
113
1188
35
95
1802
25
77
2796
15
59
4450
5
41
7280
–5
23
12300
–15
5
21450
–30
–22
52700
–40
–40
100700
DTC P1112 –IAT Sensor Circuit Intermittent Low Voltage
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to
Step 2
Go to
OBD
System
Check
2
Is DTC P0112 also set?
—
Go to
DTC
P0112 first
Go to
Step 3
3
1. Check the IAT signal circuit between the IAT sensor
connector and the PCM for an intermittent short to
ground.
2. If a problem is found, repair as necessary.
Was a problem found?
—
Verify repair
Refer to
Diagnostic
Aids
6E2–369
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1114 ECT Sensor Circuit Intermittent Low
Voltage
D06RW058
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 5.0 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 less, 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. If the PCM detects an
ECT signal that is intermittently below the range of the
ECT sensor, DTC P1114 will set.
Conditions for Setting the DTC
f
Engine run time longer than 60 seconds.
f
The ECT sensor signal is intermittently greater than
150
°
C (302
°
F) (about 0.10 volt) for a total of 10
seconds over a 100-second period.
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 DTC set as Failure Records data only. This
information will not be stored as Freeze Frame data.
Conditions for Clearing the MIL/DTC
f
A history DTC P1114 will clear after 40 consecutive
warm-up cycles have occurred without a fault.
f
DTC P1114 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:
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. 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.
Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.
6E2–370
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
Engine Coolant Temperature Sensor
°
C
°
F
OHMS
Temperature vs. Resistance Values (approximate)
100
212
177
80
176
332
60
140
667
45
113
1188
35
95
1802
25
77
2796
15
59
4450
5
41
7280
–5
23
12300
–15
5
21450
–30
–22
52700
–40
–40
100700
DTC P1114 –ECT Sensor Circuit Intermittent Low Voltage
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System Check”
performed?
—
Go to
Step 2
Go to
OBD
System
Check
2
Is DTC P0117 also set?
—
Go to
DTC
P0117 first
Go to
Step 3
3
1. Check the ECT signal circuit between the ECT
sensor connector and the PCM for an intermittent
short to ground.
2. If a problem is found, repair as necessary.
Was a problem found?
—
Verify repair
Refer to
Diagnostic
Aids
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