P0112
DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage
Circuit Description
The intake air temperature (IAT) sensor is a thermistor that controls signal voltage to the PCM. The PCM supplies a 5 V reference circuit and a ground circuit to the intake air temperature sensor. When the intake air temperature is low, the sensor's resistance is high. When the intake air temperature is high, the sensor's resistance is low.
Conditions for Running the DTC
- The engine has been running for more than 320 seconds.
- The vehicle speed sensor (VSS) indicates that the vehicle's speed is more than 15 mph (24 kph).
Conditions for Setting the DTC
The IAT sensor signal voltage indicates that the intake air temperature is above 128° C (262° F) for 3125 ms (3.125 seconds).
Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
- The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool's Freeze Frame and Failure Records.
Conditions for Clearing the MIL/DTC
- The control module turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm up cycle occurs when the coolant temperature has risen 22° C (40° F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70° C (158° F) during the same ignition cycle.
- Use the scan tool Clear Information function
Diagnostic Aids
- When the vehicle is at ambient temperature, compare the IAT sensor reading to the reading from the ECT sensor. The readings from IAT sensor and the ECT sensor should be relatively similar.
- Use the Temperature vs Resistance Values Table to evaluate the possibility of an incorrectly calibrated sensor. Refer to Temperature vs Resistance.
Steps 1 - 4:
Steps 5 - 8:
Steps 9 - 11:
Test Description
The numbers below refers to the step numbers on the Diagnostic Table.
1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
4. This step simulates a DTC P0113 condition. If the scan tool displays the specified value, the IAT signal circuit and the PCM are OK.
9. Program the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communications System (ITCS) information for PCM programming.