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 operating.

• | 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

• | 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

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 should not set.

### 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/connections test normal, replace the engine control module (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/connections test normal, replace the ECM.

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

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

### Component Testing

Measure 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 Resistance table 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 .