DTC P0112 Intake Air Temperature
(IAT) Sensor Circuit Low Voltage
The Intake Air
Temperature (IAT) sensor contains a semiconductor device which changes the
resistance based on the temperature (a thermistor).
The IAT sensor is located in the air intake passage of the engine air induction
system. The IAT sensor has a signal circuit and a ground circuit. The PCM
applies 5.0 volts on the signal circuit to the sensor. The PCM monitors
the changes in this voltage caused by changes in the resistance of the sensor
in order to determine intake air temperature.
When the intake air is
cold, the sensor (thermistor) resistance is high. The
PCMs signal voltage is only pulled down a small amount through the sensor to a
ground; therefore, the PCM senses a high signal voltage (low temperature). When
the intake air is warm, the sensor resistance is low. The signal voltage is
pulled down a greater amount; therefore, the PCM senses a low signal voltage
(high temperature).
When the PCM senses a
signal voltage lower than the normal operating range of the sensor, this DTC sets.
Conditions
for Running the DTC
- DTCs P0101, P0102, P0103, P0117,
P0118, P0125, P0500, P0502, P0503 not set.
- The engine run time is greater than
30 seconds.
- The vehicle speed at least
40 km/h (25 mph).
Conditions
for Setting the DTC
- The Intake Air Temperature is
greater than 139°C (282°F).
- All conditions met for 5.0 seconds.
Action
Taken When the DTC Sets
- The PCM illuminates the malfunction
indicator lamp (MIL) on the second consecutive ignition cycle that the
diagnostic runs and fails.
- The PCM records the operating
conditions at the time the diagnostic fails. The first time the diagnostic
fails, the PCM stores this information in the Failure Records. If the
diagnostic reports a failure on the second consecutive ignition cycle, the
PCM records the operating conditions at the time of the failure. The PCM
writes the conditions to the Freeze Frame and updates the Failure Records.
Conditions
for Clearing the MIL/DTC
- The PCM turns OFF the malfunction
indicator lamp (MIL) after 3 consecutive ignition cycles that the
diagnostic runs and does not fail.
- A last test failed, or current DTC,
clears when the diagnostic runs and does not fail.
- A history DTC clears after
40 consecutive warm-up cycles, if no failures are reported by this or
any other emission related diagnostic.
- Use a scan tool in order to clear
the MIL and the DTC.
Important
- Remove any debris from the PCM connector surfaces
before servicing the PCM. Inspect the PCM connector gaskets when
diagnosing/replacing the PCM. Ensure that the gaskets are installed
correctly. The gaskets prevent contaminate intrusion into the PCM.
- For any test that requires probing the PCM or component
harness connectors, use the Connector Test Adapter Kit J 35616-A .
Using this kit prevents any damage to the harness connector terminals.
- The following may cause an
intermittent:
- Mis-routed harness
- Rubbed through wire insulation
- Broken wire inside the insulation
- If the engine has sat overnight, the
engine coolant temperature and the engine intake air temperature values
should display within a few degrees of each other. If the temperatures are
not within 3°C (5°F), refer to Temperature vs
Resistance .
- If you determine that the DTC occurs
intermittently, performing the P1112 diagnostic table may isolate the
cause of the fault.
- For an intermittent, refer to Symptoms
.
The numbers below refer
to the step numbers on the diagnostic table.
- This step determines
if the malfunction is present. For any test that requires probing the PCM
or a component harness connector, use the Connector Test Adapter Kit J 35616-A .
Using this kit prevents damage to the harness connector terminals.
- Using the Freeze
Frame and/or Failure Records data may aid in locating an intermittent
condition. If you cannot duplicate the DTC, the information included in
the Freeze Frame and/or Failure Records data can help determine how many
miles since the DTC set. The Fail Counter and Pass Counter can also help
determine how many ignition cycles the diagnostic reported a pass and/or a
fail. Operate the vehicle within the same freeze frame conditions (RPM,
load, vehicle speed, temperature etc.) that you observed. This will
isolate when the DTC failed. For any test that requires probing the PCM or
component harness connectors, use the Connector Test Adapter Kit J 35616-A .
Using this kit prevents any damage to the harness connector terminals.
- Disconnecting the
PCM allows using the DMM J 39200 in
order to test continuity of the circuits. This aids in locating an open or
a shorted circuit.
|
Step |
Action |
Value(s) |
Yes |
No |
|
Did
you perform the Powertrain On-Board Diagnostic
(OBD) System Check? |
-- |
|||
Is
the IAT above the specified value? |
139°C (282°F) |
|||
Does
the scan tool indicate that this diagnostic failed this ignition? |
-- |
Go to Diagnostic Aids |
||
Is
the IAT at the specified value? |
-39°C (-38°F) |
|||
Is
the IAT signal circuit grounded? |
-- |
|||
|
Replace
the IAT sensor. Refer to IAT
Sensor Replacement . Is the action complete? |
-- |
-- |
||
|
Important: Program the replacement
PCM. Refer to PCM
Replacement/Programming . Replace
the PCM. Is the action complete? |
-- |
-- |
||
Does
the scan tool indicate that this test ran and passed? |
-- |
|||
|
Select
the Capture Info option and the Review Info option using the scan tool. Does
the scan tool display any DTCs that you have not diagnosed? |
-- |
Go to the applicable
DTC table |
System OK |