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| • | 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. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Air Quality Sensor Ignition | - | B3843 05 | -- | -- |
Air Quality Sensor Signal | B3843 02 | B3843 05 | B3843 05 | B3843 08 |
Air Quality Sensor Ground | - | B3843 05 | -- | -- |
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.
| • | Ignition ON. |
| • | The HVAC control module is ON. |
No PWM is detected and the signal is low.
No PWM is detected and the signal is high.
The Sensor sends a 5% PWM signal indicating an internal sensor short circuit or open circuit.
The automatic recirculation mode is disabled.
The condition for setting the DTC is no longer present.
Automatic HVAC Description and Operation
Control Module References for scan tool information
If DTC B3843 08 is present
Replace the B108 Air Quality Sensor.
If DTC B3843 08 is not present
If DTC B3843 02 or B3843 05 is present
Refer to Circuit/System Testing.
If DTC B3843 02 and B3843 05 are not present
If greater than 5 Ω
Repair the open/high resistance in the circuit.
If less than 5 Ω
If the test lamp does not illuminate and the circuit fuse is good
| 3.1. | Ignition OFF. |
| 3.2. | Test for less than 2 Ω in the ignition circuit end to end. |
If 2 Ω or greater, repair the open/high resistance in the circuit.
If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
If the test lamp does not illuminate and the circuit fuse is open
| 3.1. | Ignition OFF. |
| 3.2. | 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
If less than 95%
| 4.1. | Ignition OFF, disconnect the X1 harness connector at the K33 HVAC Control Module. |
| 4.2. | Ignition ON, 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 HVAC Control Module.
If greater than 95%
If greater than 5%
| 5.1. | Ignition OFF, disconnect the X1 harness connector at the K33 HVAC Control Module. |
| 5.2. | Ignition ON, test for less than 0.3 V between the signal circuit and ground. |
If greater than 0.3 V, repair the short to voltage on the circuit.
If less than 0.3 V
| 5.3. | Ignition OFF, test for less than 2 Ω in the signal circuit end to end. |
If 2 Ω or greater, repair the open/high resistance in the circuit.
If less than 2 Ω, replace the K33 HVAC Control Module
If less than 5%
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for HVAC control module replacement, setup, and programming |
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