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 P0110: Intake Air Temperature (IAT) Sensor Circuit
DTC P0111: Intake Air Temperature (IAT) Sensor Performance

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
IAT Sensor Signal | P0112 | P0113 | P0113* | P0110, P0111
Low Reference | -- | P0113 | P0113* | P0110, 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: Varies with ambient temperature.
IAT Sensor Signal | 130°C (266°F), | 20°C (68°F) | 20°C (68°F)*
Low Reference | -- | 20°C (68°F) | --
* Internal ECM or sensor damage may occur if the circuit is shorted to B+.

### Circuit Description

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 volts to the IAT signal circuit and a ground for the IAT low reference circuit. The ECM performs various tests to determine if the IAT is stuck in range, or out of range.

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

• | DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0502, P0562, P0563, and P2610 are not set.

• | The ignition is OFF for greater than 8 hours.

• | The engine is running.

#### P0110 - Idle Test

- | The vehicle speed is less than 2 km/h (1.2 mph).

- | The throttle position (TP) sensor is less than 2 percent.

- | The engine is operating at idle.

- | The above conditions are met for greater than 60 seconds.

#### P0110 - Cruise Test

- | The vehicle speed is greater than 40 km/h (25 mph).

- | The mass air flow (MAF) sensor is greater than 15 g/s.

- | The engine is operating at a cruise.

- | The above conditions are met for greater than 300 seconds.

#### P0111 - Skew High Test

- | The calculated engine airflow is greater than 15 g/s.

- | The vehicle speed is greater than 40 km/h (25 mph).

#### P0111 - Skew Low Test

- | The calculated engine airflow is greater than 15 g/s.

- | The vehicle speed is greater than 40 km/h (25 mph).

- | The start-up engine coolant temperature (ECT) minus the start-up intake air temperature (IAT) is greater than 20°C (36°F).

- | The start-up ECT is greater than -20°C (-4°F).

• | The DTCs run once an ignition cycle once the above conditions are met.

### Conditions for Setting the DTC

#### P0110

• | Cruise Test - The ECM does not detect an intake air temperature (IAT) change of greater than 3°C (5°F).

• | Startup Test - The ECM does not detect a difference of 3°C (5°F) between the previous ignition cycle IAT and the start-up IAT of the next ignition cycle.

#### P0111

• | Skew High Test - The ECM detects a 20°C (36°F) difference between the start-up IAT and the start-up engine coolant temperature.

• | Skew Low Test - The ECM detects a 20°C (36°F) difference between the start-up engine coolant temperature and the start-up IAT.

### Action Taken When the DTC Sets

DTCs P0110 and P0111 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0110 and P0111 are Type B DTCs.

### Diagnostic Aids

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

• | The use of the engine block heater may cause DTC P0111 to set. Verify with the customer whether the block heater was in use prior to the DTC setting.

### 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 running, observe the DTC information with a scan tool. DTCs P0112, P0113, P0115, P0117, P0118, P0125, P0128 should not set.

⇒ | If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

2. Observe the DTC information with a scan tool. DTCs P0110 or P0111 should not set.
3. 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 IAT sensor.
2. Ignition ON, clear the DTC information with a scan tool.
3. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 1 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 ECM.

4. Ignition ON, clear the DTC information with a scan tool.
5. Verify the scan tool IAT sensor parameter is at -40°C (-40°F).

⇒ | If greater than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

6. Connect a 3A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1. Verify the scan tool IAT sensor parameter is greater than 128°C (262°F).

⇒ | If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

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

### Component Testing

1. Ignition OFF, disconnect the harness connector at 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 table and verify the resistance is within 5 percent of the specification.

⇒ | If the resistance Vs. temperature is not within the specified range, replace the IAT sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Intake Air Temperature Sensor Replacement

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