HVAC - Automatic

Exhaust Odor Inside Vehicle

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions)provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit Description

The HVAC control module monitors the outside air quality via the air quality sensor assembly while in AUTO mode. The air quality sensor is a 5-wire sensor with a single ignition voltage circuit, a ground circuit, a low reference circuit, and two signal circuits. There are 2 sensors inside the air quality sensor assembly. A hydrocarbon (HC) sensor which is used for detecting gasoline exhaust fumes and a NOX sensor which is used for detecting oxides of nitrogen. When high levels of HC are detected at the front of the vehicle the HC sensor resistance and signal voltage are low. When high levels of NOX are detected at the front of the vehicle the Nox sensor resistance and signal voltage are high.

Reference Information
Schematic Reference

HVAC Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Automatic HVAC Description and Operation (HVAC - Automatic)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the air quality sensor.
2. Test for less than 5 ohms between the ground circuit terminal 6 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

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 test normal test or replace the HVAC control module.

4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

5. Test for 4.8-5.2 volts between the ground circuit terminal 6 and the signal circuit terminal 4.

• If less than the specified range, test the signal circuit for a open/high resistance. If the circuit tests normal, replace the HVAC control module.

6. Test for 4.8-5.2 volts between the ground circuit terminal 6 and the signal circuit terminal 2.

• If less than the specified range, test the signal circuit for a open/high resistance. If the circuit tests normal, replace the HVAC control module.

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

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Outside Air Quality Sensor Replacement (Service and Repair)
* Control Module References (Programming and Relearning)for HVAC control module replacement, setup, and programming