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 1 Circuit
DTC P0110 09: Intake Air Temperature (IAT) Sensor 1 Circuit Rate of Change Above Threshold
DTC P0110 0A: Intake Air Temperature (IAT) Sensor 1 Circuit Rate of Change Below Threshold
DTC P0110 11: Intake Air Temperature (IAT) Sensor 1 Circuit Above Maximum Threshold
DTC P0110 12: Intake Air Temperature (IAT) Sensor 1 Circuit Below Minimum Threshold

### Circuit Description

The intake air temperature (IAT) sensor 1 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

• | The ignition is ON or the engine is running.

• | The ignition voltage is greater than 8.5 volts.

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

### Conditions for Setting the DTC

#### P0110

The ECM detects that an IAT 1 circuit is open, shorted to ground or voltage.

#### P0110 11

The ECM detects that the duty cycle of IAT 1 signal is greater than 90 percent.

#### P0110 12

The ECM detects that the duty cycle of IAT 1 signal is less than 10 percent.

### Action Taken When the DTC Sets

DTC P0110 is a Type B DTC.

### Conditions for Clearing the MIL/DTC

DTC P0110 is a Type B DTC.

### Diagnostic Aids

• | If the engine 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. Ignition ON, observe the DTC information with a scan tool. DTC P0110 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, and the MAIN fuse removed, disconnect the harness connector at the MAF/IAT sensor.
2. Test for less than 5 ohms of resistance between the low reference circuit terminal 2 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 tests normal, replace the ECM.

3. Install the MAIN fuse. Ignition ON, test for 4.8-5.2 volts between the IAT signal circuit terminal 3 and ground.

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

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

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

### Component Testing

Test and record the resistance between the signal circuit terminal 3 and the low reference circuit terminal 2 at various ambient temperatures. Compare those measurements to the Temperature Versus Resistancetable and verify that the resistance is within 5 percent of the specification.

⇒ | If not within the specified range, replace the MAF/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

### Repair Verification

Ignition ON, observe the scan tool DPF soot mass parameter. The parameter should be less than 24 grams.

⇒ | If greater than the specified range, perform a DPF service regeneration. Refer to Exhaust Particulate Filter Cleaning.