B2496

DTC B2496 or B3843

Diagnostic Instructions

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



DTC Descriptors
DTC B3843 02
- Outside Air Quality Sensor 2 Circuit Short to Ground

DTC B2496 02
- Outside Air Quality Sensor 1 Circuit Short to Ground




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, 1 ignition voltage circuit, 2 ground circuits and 2 signal circuits. There are 2 sensors inside the air quality sensor assembly. A hydro carbon (HC) sensor which is used for detecting gasoline exhaust fumes and a Nox sensor which is used for detecting nitrous of oxide. When high levels of hydro carbons (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.


Conditions for Running the DTC

* The ignition is ON
* DTC B1325 must not be present.



Conditions for Setting the DTC

The HVAC control module detects the air quality sensor signal that is less than 0.09 volts for more than 30 seconds


Action Taken When the DTC Sets

The driver information center (DIC) will display SERVICE A/C SYSTEM.


Conditions for Clearing the DTC

* The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
* The history DTC will clear after 50 fault-free ignition cycles.



Reference Information
Schematic Reference

HVAC Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Automatic HVAC Description and Operation (Automatic HVAC Description and Operation (Part 1))
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

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 of resistance between the ground circuit terminal 6 and ground.

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

3. Test for less than 5 ohms of resistance 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.

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