B3843
DTC B3843
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.
DTC Descriptors
DTC B3843 02
-
Air Quality Sensor Circuit Short to Ground
DTC B3843 05
-
Air Quality Sensor Circuit High Voltage/Open
DTC B3843 08
-
Air Quality Sensor Circuit Performance - Signal Invalid
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 information is pulse width modulation (PWM) signal generated on the output pin.
The HVAC control module evaluates the information of the air quality sensor and closes the recirculation flap 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 02
No PWM is detected and the signal is low.
B3843 05
No PWM is detected and the signal is high.
B3843 08
The sensor sends a 5% PWM signal indicating an internal sensor short circuit or open circuit.
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 Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Automatic HVAC Description and Operation Description and Operation
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 Control Module References
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF. Disconnect the B108 air quality sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 2 and ground.
• If 10 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms
3. Ignition ON.
4. Verify a test lamp illuminates between the ignition circuit terminal 1 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 ohms in the ignition circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is OK and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the ignition circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the B108 air quality sensor.
• If the test lamp illuminates
5. Verify the scan tool Odor Sensor parameter is greater than 95%.
• If 95% or less
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module.
2. Test for infinite resistance between the signal circuit terminal 3 and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K33 HVA Ccontrol module.
• If greater than 95%
6. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal 2.
7. Verify the scan tool Odor Sensor parameter is less than 5%.
• If 5% or greater
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 3 and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Ignition OFF
4. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K33 HVAC control module.
• If less than 5%
8. If all circuits test normal, replace the B108 air quality sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* HVAC Component Replacement Reference Removal and Replacement
* Control Module References Control Module References for HVAC control module replacement, programming and setup