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 provide 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 | P0113¹ | P0110, P0111
Low Reference | -- | P0113 | P0113¹ | P0110, 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: Varies with ambient temperature
IAT Sensor Signal | 141°C (286°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 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 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 more than 60 seconds.

#### P0110-Cruise Test

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

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

- | The engine is operating at a cruise.

- | The above conditions are met for more 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 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 ECT.

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

### Action Taken When the DTC Sets

DTC P0110 and P0111 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTC 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

• | 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

### Circuit/System Verification

1. Verify that the following DTCs are not set: P0112, P0113, P0115, P0117, P0118, P0125, P0128.

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

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. DTC P0110 or P0111 should not set.
3. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the IAT sensor.
2. Ignition ON, clear the DTC information with a scan tool.
3. Ignition ON, verify that the scan too 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 ECM.

4. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit and ground.

⇒ | If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.

5. Ignition ON, clear the DTC information with a scan tool.

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

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

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

7. If all circuits/connections test normal, test or replace the 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 table and verify that the temperature 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.

• | Air Cleaner Inlet Duct Replacement

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