B3843

DTC B2496 or B3843

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 control 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 oxide, diesel exhaust fumes. 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.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

* DTC B2496 Nox Sensor Circuit (Outside Air Quality Sensor 2 Circuit)
* DTC B3843 Hydro Carbon Sensor Circuit (Outside Air Quality Sensor 1 Circuit)






Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

The HVAC control module detects the air quality sensor signal circuit is less than 0.09 volt (5 counts).

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 a failure.
* The history DTC will clear after 50 fault-free ignition cycles.
* The DTC can be cleared with a scan tool.

Diagnostic Aids

If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Diagnostic Aids. Component Tests and General Diagnostics

Test Description

Step 1 - Step 9:

The numbers below refer to the step numbers on the diagnostic table.
3. Tests for the proper operation of the circuit in the low voltage range.
4. Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
5. Tests for a short to voltage in the 5-volt reference circuit.