For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC P0112 00: Intake Air Temperature (IAT) Sensor Circuit Low Voltage
DTC P0113 00: Intake Air Temperature (IAT) Sensor Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to voltage | Signal Performance
--- | --- | --- | --- | ---
IAT sensor signal | P0112 00, | P0113 00, | P0113 00, | --
Low reference | -- | P0113 00, | P0113 00, | --

### Typical Scan Tool Data

#### IAT Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine operating in closed loop Parameter Normal Range: Varies with ambient temperature
IAT sensor signal | 150°C (302°F) | -40°C (-40°F)* | -40°C (-40°F)
Low reference | -- | -40°C (-40°F)* | -40°C (-40°F)
* Internal ECM or sensor damage may occur if the circuit is shorted to B+.

### Circuit/System Description

The intake air temperature (IAT) sensor is an integral part of the mass air flow (MAF) sensor. The intake air temperature (IAT) sensor is a variable resistor that measures the temperature of the air entering the engine. The IAT sensor has a signal circuit and a low reference circuit. The engine control module (ECM) supplies 5 V to the IAT signal circuit and a ground for the IAT low reference circuit.

The following table illustrates the difference between temperature, resistance, and voltage:

IAT | IAT Resistance | IAT Signal Voltage
--- | --- | ---
Cold | High | High
Warm | Low | Low

### Conditions for Running the DTC

#### P0112 00

• | DTCs P0117 00, or P0118 00, are not set

• | The engine run time is greater than 10 s.

• | The engine coolant temperature (ECT) sensor is less than 150°C (302°F).

• | The vehicle speed is greater than 0 km/h (0 MPH).

• | The DTC runs continuously once the above conditions are met.

#### P0113 00

• | DTCs P0107 00, P0108 00, P0117 00, or P0118 00, are not set.

• | The engine run time is greater than 10 s.

• | The airflow into the engine is less than 512 g/s.

• | The engine coolant temperature (ECT) sensor is greater than -40°C (-40°F).

• | The vehicle speed is less than 512 km/h (318 MPH).

• | The DTC runs continuously once the above conditions are met.

### Conditions for Setting the DTC

#### P0112 00

The ECM detects that the IAT sensor is greater than 149°C (300°F) for greater than 10 s.

#### P0113 00

The ECM detects that the IAT sensor parameter is colder than -40°C (-40°F) for greater than 4 s.

### Action Taken When the DTC Sets

DTCs P0112 00 and P0113 00 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0112 00 and P0113 00 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Engine idling, observe the DTC information with a scan tool. DTCs P0112 00 or P0113 00 should not set.
2. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the freeze frame / failure records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B75B Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor.
2. Ignition OFF for 90 s, test for less than 5 Ω between the low reference circuit terminal B and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open / high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

3. Ignition ON, verify the scan tool IAT Sensor is colder than -40°C (-40°F).

⇒ | If warmer than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.

4. Install a 3 A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool IAT Sensor is greater than 149°C (300°F).

⇒ | If less than the specified range, test the signal circuit for a short to voltage or an open / high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. If all circuits test normal, test or replace the B75B Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Mass Airflow Sensor Replacement

• | Control Module References for ECM replacement, setup, and programming