2010 Cadillac CTS Sedan AWD V6-3.6L Page 626
Diagnostic Fault Information
Circuit/System Description
The HVAC control module detects exhaust gas by an air quality sensor. The air quality sensor is a 3-wire sensor with an ignition voltage circuit, a
ground circuit and a signal circuit.
The sensor outputs a PWM Signal to the HVAC control module with different levels of pollution as detected outside.
The HVAC control module evaluates the information of the air quality sensor and closes the recirculation door while in the automatic mode as soon
as the concentration of pollutants exceeds a preset value.
Conditions for Running the DTC
* Ignition ON.
* The HVAC control module is ON.
Conditions for Setting the DTC
B3843 00
If the PWM signal is greater than 97% for more than 30 seconds.
B3843 02
No PWM is detected and the signal is low for more than 30 seconds.
B3843 05
No PWM is detected and the signal is high for more than 30 seconds.
B3843 21
PWM signal is detected but the frequency is outside of the valid range for more than 30 seconds.
Action Taken When the DTC Sets
The automatic recirculation mode is disabled.
Conditions for Clearing the DTC
The condition for setting the DTC is no longer present.
Reference Information
Schematic Reference
HVAC Schematics (See: Heating and Air Conditioning/Diagrams/Electrical Diagrams)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Automatic HVAC Description and Operation (See: Heating and Air Conditioning/Description and Operation/HVAC - Automatic)
Electrical Information Reference
* Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit Testing/Circuit Testing)
* Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Connector Repairs/Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit
Testing/Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Wiring Repairs/Wiring Repairs)
