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 P0111: Intake Air Temperature (IAT) Sensor Performance

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
IAT Sensor Signal | P0112, P0114 | P0113, P0114 | P0113, P0114 | P0113, P0114 | P0111, P0114
Low Reference | -- | P0113, P0114 | P0113, P0114 | P0113, P0114 | P0111, P0114

### Typical Scan Tool Data

#### IAT Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: The ignition is ON, or the engine is running Parameter Normal Range: Varies with ambient temperature
IAT Sensor Signal | 129°C (264°F) | -40°C (-40°F) | -40°C (-40°F)
Low Reference | -- | -40°C (-40°F) | -40°C (-40°F)

### Circuit/System Description

The intake air temperature (IAT) sensor is integrated with the mass air flow (MAF) sensor. The IAT sensor is a variable resistor that measures the temperature of the air when it first enters the induction system. The engine control module (ECM) supplies 5 volts to the IAT signal circuit and a ground for the shared MAF/IAT low reference circuit.

The purpose of this diagnostic is to analyze the performance of the IAT sensor by comparing the response and the range of the sensor signal to two distinct models under various operating conditions.

• | The first model verifies that the sensor is not stuck in range.

• | The second model verifies that the sensor is within an acceptable operating range of the calculated IAT.

| Both models use various parts of the information derived from the following inputs:

- | Ambient air temperature (AAT)

- | Barometric (BARO) pressure

- | Distance driven

- | Engine coolant temperature (ECT)

- | Engine OFF time

- | Engine run time

- | IAT

- | MAF

- | Throttle position (TP)

- | Vehicle speed (VS)

### Conditions for Running the DTC

#### P0111 - Engine Running, Sensor Stuck in Range Test

• | DTC P0068, P0101, P0112, P0113, P0114, P0116, P0117, P0118, P0119, P0501, or P1101 is not set.

• | The Ambient Temperature parameter is warmer than 8°C (46°F).

• | The distance driven is greater than 10 km (6 miles).

• | The ECT is warmer than 69°C (156°F).

• | The engine is running.

• | The engine run time is greater than 600 seconds.

• | The ignition voltage is greater than 9 volts.

• | This DTC runs continuously within the enabling conditions.

#### P0111 - Engine Running, Sensor Within Range Test

• | DTC P0068, P0072, P0073, P0074, P0101, P0102, P0103, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0119, P0335, P0336, P0340, P0341, P0365, P0366, P0501, P1101, P2227, P2228, or P2229 is not set.

• | The engine is running.

• | The engine OFF timer is greater than 460 minutes.

• | The engine run time is between 60-120 seconds.

• | The ignition voltage is greater than 9 volts.

• | The AAT at engine start, minus AAT of the moving vehicle, is within a calibrated range.

• | The ECT at engine start, minus ECT of the moving vehicle, is within a calibrated range.

• | The IAT at engine start, minus IAT of the moving vehicle, is within a calibrated range.

• | The VS is greater than 16 km/h (10 mph) for greater than 20 seconds.

• | This DTC runs once per drive cycle within the enabling conditions.

### Conditions for Setting the DTC

#### P0111 - Engine Running, Sensor Stuck in Range Test

The ECM detects that the amount of change in the IAT sensor signal since engine start is not within a calibrated range of the model for greater than 2 seconds.

#### P0111 - Engine Running, Sensor Within Range Test

The ECM detects that the IAT sensor signal either warmer or colder is not within a calibrated range of the model for greater than 2 seconds.

### Action Taken When the DTC Sets

DTC P0111 is a Type B DTC.

### Conditions for Clearing the MIL/DTC

DTC P0111 is a Type B DTC.

### Diagnostic Aids

• | When the engine is cold, at ignition ON, a properly functioning IAT sensor will gradually increase the scan tool IAT Sensor parameter. This is due to the heat that is generated by the MAF sensor heating elements.

• | Depending on the ambient temperature, an IAT sensor signal circuit that is shorted to the MAF sensor signal circuit may cause either a rapid fluctuation in the IAT Sensor parameter or cause it to become stuck at a given value.

### 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

• | If the ignition has been OFF for 8 hours or greater, the IAT, the ambient temperature, and the engine coolant temperature (ECT) should be within 9°C (16°F) of each other. Ignition ON, observe the scan tool IAT Sensor, Ambient Temperature, and the ECT Sensor parameters. Compare those sensor parameters to each other to determine if the condition is current.

• | Ignition OFF for 90 seconds, determine the current vehicle testing altitude. Ignition ON, observe the scan tool BARO Sensor parameter. Compare the parameter to the Altitude Versus Barometric Pressure table. The parameter should be within the specified range indicated in the table. If the parameter is not within range, refer to DTC P2227, P2228, or P2229.

• | Engine operating at idle, observe the scan tool MAF Sensor parameter. The reading should be between 2-8 g/s.

• | Drive the vehicle under various operating conditions. Observe the scan tool IAT Sensor parameter and the Ambient Temperature parameter. The readings should be near each other.

• | Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Inspect the MAF/IAT sensor elements for contamination, and debris.
2. Ignition OFF for 90 seconds, disconnect the harness connector at the MAF/IAT sensor.
3. Test for less than 5 ohms between the IAT sensor low reference circuit terminal 1 and ground.

⇒ | If greater than the specified range, test the low reference circuit for a high resistance.

4. Disconnect the ECM.
5. Test the IAT signal circuit between terminal 2 and ECM connector X 1 terminal 12 for less than 5 ohms.

⇒ | If greater than the specified range, test the signal circuit for a high resistance.

6. If the circuits test normal, test or replace the IAT sensor.

### Component Testing

Measure and record the resistance of the IAT sensor at various ambient temperatures, then compare those measurements to the Temperature vs Resistance table. Refer to Temperature Versus Resistance.

### 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