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 | P0113* | P0111
Low Reference | -- | P0111, P0113 | P0113* | P0111
* 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)*
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 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.

• | DTC P0112, P0113, P0116, P0117, P0118, P0119, or P0128 is not set.

• | The engine coolant temperature (ECT) at engine start is colder than 110°C (230°F).

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

• | The vehicle speed is less than 11 km/h (7 mph).

• | The MAF is less than 8 g/s.

• | DTC P0111 runs continuously once the above conditions are met for approximately 300 seconds, depending on the drive cycle.

#### P0111 Cruise Test

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

• | DTC P0112, P0113, P0116, P0117, P0118, P0119, or P0128 is not set.

• | The ECT at engine start is colder than 110°C (230°F).

• | The vehicle speed is greater than 29 km/h (18 mph).

• | The MAF is between 7-67 g/s.

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

• | DTC P0111 runs continuously once the above conditions are met for approximately 300 seconds, depending on the drive cycle.

#### P0112 and P0113

• | The vehicle speed is less than 3 mph.

• | The ECT is warmer than -10°C (14°F).

• | The MAF is less than 28 g/s.

• | The DTCs runs continuously once the above conditions are met for greater than 2 seconds.

### Conditions for Setting the DTC

#### P0111

The ECM detects that the IAT remains steady within 2°C (4°F) during the idle test. Or, the ECM detects that the IAT decreased less than 2°C (4°F) during the cruise test. The condition exists for greater than 4 seconds or for a cumulative of 30 seconds.

#### P0112

The ECM detects that the IAT sensor voltage is greater than 4.87 volts for greater than 1 second or for a cumulative 10 seconds.

#### P0113

The ECM detects that the IAT sensor voltage is less than 0.21 volts for greater than 1 second or for a cumulative 10 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.

### 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, DTC P0111, P0112, or P0113 should not set.
2. 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. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
2. Remove the fuse that supplies B+ to circuit terminal X2-56 of the ECM.

Caution: 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.

3. Test for less than 5 Ω between the low reference circuit terminal E and ground.

⇒ | If greater than the specified range, 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.

4. Install the fuse that supplies B+ to circuit terminal X2-56 of the ECM.
5. Ignition ON, verify that the scan tool IAT sensor parameter is at -40°C (-40°F).

⇒ | If greater than the specified value, test the signal circuit for a short to ground. If the circuit/connections test normal, replace the 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.

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

⇒ | If colder 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 at the IAT sensor.

Note: 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 % of the specification.

⇒ | If the not within the specified range, 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