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. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Air Quality Sensor B+ | 1 | 1 | -- | -- |
Hydrocarbon Sensor Signal | B3843 02 | 1 | 1 | 1 |
NOX Sensor Signal | B2496 02 | 1 | 1 | 1 |
Low Reference | -- | 1 | -- | -- |
Air Quality Sensor Ground | -- | 1 | -- | -- |
1. Exhaust Odor In Vehicle | ||||
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
Connector End View Reference
Description and Operation
Automatic HVAC Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the air quality sensor.
- Test for less than 5 ohms between the ground circuit terminal 6 and ground.
- Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 1 and ground.
- Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.
- Test for 4.8-5.2 volts between the ground circuit terminal 6 and the signal circuit terminal 4.
- Test for 4.8-5.2 volts between the ground circuit terminal 6 and the signal circuit terminal 2.
- If all circuits test normal, test or replace the air quality sensor.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | 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. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | 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. |
| ⇒ | 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for HVAC control module replacement, setup, and programming |
