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 Descriptor

DTC 8: Intake Sensor Error

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Intake Sensor Signal | 8 | 8 | 8 | 8
Ground | -- | 8 | -- | 8

### Circuit/System Description

The HVAC intake sensor monitors the temperature of the fresh air in the air inlet by way of a sensor circuit that sends a signal to the Heating Ventilation and Air Conditioning (HVAC) module.

### Conditions for Running the DTC

• | The engine must be running.

• | The HVAC control unit must be ON.

### Conditions for Setting the DTC

This DTC will set if the output of the in-car sensor indicates a short circuit or an open in the sensor or the associated wiring harness, or a malfunction in the HVAC controller.

### Action Taken When the DTC Sets

• | The HVAC system stays in a default mode until the fault is cleared.

• | The diagnostic code remains on the display.

### Conditions for Clearing the DTC

The diagnostic code automatically clears after the fault has been rectified.

### Reference Information

#### Schematic Reference

HVAC Schematics

#### Connector End View Reference

HVAC Connector End Views

#### Description and Operation

Automatic HVAC Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Verification

Engine running, observe the HVAC control display. The HVAC control unit should be able to be adjusted to the desired temperature.

### Circuit/System Testing

1. Ignition OFF, disconnect the intake sensor harness connector at the HVAC controller.
2. Ignition OFF, test for less than 1.0 ohm 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. If the circuit tests normal, replace the HVAC controller.

3. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 1 and low reference circuit terminal 2.

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

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

4. If all circuits test normal, test or replace the intake air sensor.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the intake sensor.
2. Test for 7080-8080 ohms of resistance between the signal terminal 1 and the low reference circuit terminal 2.

⇒ | If not within the specified range, replace the intake air sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Heater and Air Conditioning Control Replacement