P0112

DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage:

Intake Air Temperature (IAT) Sensor:

CIRCUIT DESCRIPTION

The Intake Air Temperature (IAT) sensor is a thermistor (a variable resistor that changes along with outside air temperature) in series with a fixed resistor in the Engine Control Module (ECM). The ECM applies 5 volts to the IAT sensor. The ECM monitors the voltage across the IAT sensor and converts it into a temperature reading. When the outside air temperature is cold the IAT sensor resistance is high, and when the outside air temperature is warm the IAT sensor resistance is low. Therefore, when the air temperature is cold the ECM will receive a high voltage input, and when the air temperature is warm the ECM will receive a low voltage input.

CONDITIONS FOR SETTING THE DTC

- Engine Running.

- IAT signal voltage indicates an intake air temperature greater than 139°C (282°F).

- The above condition is met for at least 5 seconds.

ACTION TAKEN WHEN THE DTC SETS

- The Malfunction Indicator Lamp (MIL) will illuminate.

- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

CONDITIONS FOR CLEARING THE MIL/DTC

- The MIL will turn "OFF" after three consecutively passing cycles without a fault present.

- A History DTC will clear after 40 consecutive warm-up cycles without a fault.

- DTC(s) can be cleared by using a scan tool or by disconnecting the ECM battery feed.

DIAGNOSTIC AIDS

Check the following conditions:

- Poor connection at ECM. Inspect harness connectors for backed out terminal, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

- Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the IAT display on the scan tool while moving connectors and wiring harnesses related to the IAT sensor. A change in the IAT display will indicate the location of the fault.

- When replacing the IAT sensor the "Temperature to Resistance Value" scale may be used to test the sensor at various temperature levels to evaluate the possibility of a "shifted" (mis scaled) sensor. A "shifted" sensor could result in poor driveability complaints. Refer to IAT sensor specifications.

If DTC P0112 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

If any wiring repairs need to be made, Refer to Repair Procedures in Diagrams.

TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Engine OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. Determines if fault is present.

3. Review Freeze Frame data to determine when the DTC set. Always record this information.

4. This step determines if the fault is caused by a shorted signal return circuit or by a malfunctioning IAT sensor.