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 Descriptors

DTC P0111: Intake Air Temperature (IAT) Sensor Circuit Performance
DTC P0112: Intake Air Temperature (IAT) Sensor Circuit Low Voltage
DTC P0113: 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 | P0111, P0113 | P0113¹ | P0111
Low Reference | -- | P0111, P0113 | P0113¹ | P0111
¹ Internal ECM or sensor damage may occur if the circuit is shorted to B+

### Typical Scan Tool Data

#### IAT Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine operating in Closed Loop. Parameter Normal Range: -39° to +134°C (-38° to +274°F) Varies with ambient temperature.
IAT Sensor Signal | 135°C (275°F) | -40°C (-40°F) | -40°C (-40°F)¹
Low Reference | -- | -40°C (-40°F) | -40°C (-40°F)¹
¹ Internal ECM or sensor damage may occur if the circuit is shorted to B+

### Circuit Description

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

#### P0111 Idle Test

• | Before the ECM can report DTC P0111 failed, DTC P0101 must run and pass.

• | DTCs P0112, P0113, P0116, P0117, P0118, P0119, P0125, and P0128 are not set.

• | The engine coolant temperature (ECT) at engine start is less than 85°C (185°F).

• | The ECT is more than 66°C (151°F).

• | The vehicle speed is less than 10 km/h (6 mph).

• | DTC P0111 runs continuously once the above conditions are met for more than 2 seconds.

#### P0111 Cruise Test

• | Before the ECM can report DTC P0111 failed, DTC P0101 must run and pass.

• | DTCs P0112, P0113, P0116, P0117, P0118, P0119, P0125, and P0128 are not set.

• | The ECT at engine start is less than 85°C (185°F).

• | The vehicle speed is more than 40 km/h (25 mph).

• | The MAF is between 11-42 g/s.

• | Decel fuel cut-off (DFCO) is not active.

• | DTC P0111 runs continuously once the above conditions are met for more than 2 seconds.

#### P0112 and P0113

• | The engine run time is more than 3 minutes.

• | The engine is idling for more than 10 seconds.

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

### Conditions for Setting the DTC

#### P0111

The ECM detects that the IAT remains steady within 2°C (4°F) during the idle test. The condition exists for a total of 16 seconds. Or, the ECM detects that the IAT decreased less than 2°C (4°F) during the cruise test. The condition exists for a total of 28 seconds.

#### P0112

The ECM detects that the intake air temperature is more than 132°C (270°F) for more than 4 seconds or cumulative of 50 seconds.

#### P0113

The ECM detects that the intake air temperature is less than -42°C (-43.6°F) and remains steady within 3°C (5°F) during an air flow increase of more than 999 grams. The scan tool is limited to -40°C (-40°F), so the diagnostic procedure uses -39°C (-38°F) to determine if there is an IAT condition. The condition exists for more than 4 seconds or cumulative of 50 seconds.

### Action Taken When the DTC Sets

DTCs P0111, P0112, and P0113 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0111, P0112, and P0113 are Type B DTCs.

### Diagnostic Aids

• | If the vehicle has sat overnight, the IAT sensor and the ECT sensor values should display within 3°C (5°F).

• | High resistance on either the IAT sensor signal circuit or the IAT sensor low reference circuit could set a DTC.

• | Use the J 35616 Connector Test Adapter Kit for any test that requires probing the underhood fuse block terminals, component wire harness terminals, or the ECM wire harness connector terminals.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

#### Special Tools Required

J 35616 Connector Test Adapter Kit

### Circuit/System Verification

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. DTC P0111, P0112, or P0113 should not set.

### Circuit/System Testing

1. Ignition OFF, disconnect the MAF/IAT sensor.
2. Ignition ON, verify that the IAT sensor parameter is at -40°C (-40°F).

⇒ | If greater than -40°C (-40°F), test the signal circuit for a short to ground. If the circuit/connections test normal, replace the engine control module (ECM).

3. Ignition OFF, remove the fuse that supplies B+ to circuit terminal C2-56 of the ECM.

Notice: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.

4. Test for less than 5 ohms between the low reference circuit terminal E and ground.

⇒ | If greater than 5 ohms, test the low reference circuit for an open/high resistance, or for a short to voltage. If the circuit/connections test normal, replace the ECM.

5. Install the fuse that supplies B+ to circuit terminal C2-56 of the ECM.

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

6. Ignition ON, install a 3A fused jumper wire between the signal circuit terminal D and ground circuit terminal C. Verify the IAT sensor parameter is greater than 134°C (274°F).

⇒ | If less than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit/connections test normal, replace the ECM.

7. If all circuits/connections test normal, test or replace the MAF/IAT sensor.

### Component Testing

1. Ignition OFF, disconnect the harness connector of the IAT sensor.

Important: A thermometer can be used to test the sensor off the vehicle.

2. Test the IAT sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the Temperature Versus Resistance - Intake Air Temperature Sensor table and verify that the resistance is within 5 percent of the specification.

⇒ | If the Resistance vs Temperature is not within 5 percent, replace the IAT sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Mass Airflow Sensor/Intake Air Temperature Sensor Replacement

• | Control Module References for engine control module replacement, setup, and programming