B0423
DTC B0248, B0268, B0408, B0413, B0418, B0423, B3761, or B3773
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 the diagnostic category.
DTC Descriptors
DTC B0248 61
- Air Flow Control 3 Circuit Actuator Stuck
DTC B0268 61
- Air Flow Control 7 Circuit Actuator Stuck
DTC B0408 61
- Temperature Control 1 Circuit Actuator Stuck
DTC B0413 06
- Temperature Control 1 Feedback Circuit Short to Ground or Open
DTC B0418 61
- Temperature Control 2 Circuit Actuator Stuck
DTC B0423 06
- Temperature Control 2 Feedback Circuit Short to Ground or Open
DTC B3761 06
- Air Flow Control 3 Feedback Circuit Short to Ground or Open
DTC B3773 06
- Air Flow Control 7 Feedback Circuit Short to Ground or Open
Diagnostic Fault Information
Circuit/System Description
The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator consists of an electric motor and a potentiometer. The module supplies a low reference and 5-volt reference source voltage to the potentiometer. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. When the actuator shaft rotates, the voltage on the door position signal circuit changes. The HVAC module controls the direction of the actuator door by changing the polarity of the control circuits.
* Air Flow Control 3 is the mode actuator
* Air Flow Control 7 is the recirculation actuator
* Temperature Control 1 is the left temperature actuator
* Temperature Control 2 is the right temperature actuator
Conditions for Running the DTC
* Ignition ON.
* Ignition voltage is between 9-16 volts.
* The HVAC module is ON.
Conditions for Setting the DTC
The actual door position differs from the commanded door position by more than 4 counts or the HVAC control module detects the door position signal circuit is less than 7 counts or greater than 250 counts.
Action Taken When the DTC Sets
Control A and control B circuits are deactivated for the appropriate actuator.
Conditions for Clearing the DTC
* The DTC becomes history when 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 HVAC - Automatic
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 for scan tool information
Circuit/System Verification
Ignition ON, command the appropriate actuator to 100 percent with a scan tool. The scan tool should display between 224 and 230 counts on the mode actuator, all other actuators should display between 199 and 205 counts.
Circuit/System Testing
1. Ignition OFF, disconnect the X1 harness connector at the HVAC control module.
2. Ignition ON, Verify that a test lamp illuminates between the B+ circuit terminal 18 and ground.
• If the test lamp does not illuminate, test the B+ circuit for an short to ground or a open/high resistance.
3. Ignition OFF, connect the harness connector at the HVAC control module and disconnect the harness connector at the appropriate actuator.
4. Ignition OFF, test for less than 10 ohms between the following low reference circuit terminal and ground.
* Air temperature actuator-left terminal 1
* Air temperature actuator-right terminal 2
* Mode actuator terminal 2
* Recirculation actuator terminal 1
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
5. Ignition ON, test for 4.8-5.2 volts between the following 5-volt reference circuit terminal and ground.
* Air temperature actuator-left terminal 2
* Air temperature actuator-right terminal 1
* Mode actuator terminal 1
* Recirculation actuator terminal 3
• If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
• If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
6. Verify the scan tool Door Position parameter is greater than 250 counts.
• If less than the specified range, test the following signal circuit for a short to ground. If the circuit tests normal, replace the HVAC control module.
* Air temperature actuator-left terminal 3
* Air temperature actuator-right terminal 3
* Mode actuator terminal 3
* Recirculation actuator terminal 5
7. Install a 3A fused jumper wire between the following signal circuit terminal and the low reference circuit terminal. Verify the scan tool Door Position parameter is less than 3 counts.
* Air temperature actuator-left terminal 3 and terminal 1
* Air temperature actuator-right terminal 3 and terminal 2
* Mode actuator terminal 3 and terminal 2
* Recirculation actuator terminal 5 and terminal 1
• If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
8. Ignition OFF, test for less than 10 ohms between the following control circuit terminal and ground.
* Air temperature actuator-left terminal 5
* Air temperature actuator-right terminal 5
* Mode actuator terminal 5
* Recirculation actuator terminal 6
• If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the HVAC control module.
9. Ignition OFF, test for less than 10 ohms between the following control circuit terminal and ground.
* Air temperature actuator-left terminal 4
* Air temperature actuator-right terminal 4
* Mode actuator terminal 4
* Recirculation actuator terminal 7
• If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the HVAC control module.
10. Connect a test lamp between following control circuit terminals.
* Air temperature actuator-left terminal 5 and terminal 4
* Air temperature actuator-right terminal 5 and terminal 4
* Mode actuator terminal 5 and terminal 4
* Recirculation actuator terminal 6 and terminal 7
11. Ignition ON, command the appropriate actuator door in both directions with a scan tool. The test lamp should turn ON and OFF when commanded in both directions.
• If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the HVAC control module.
12. If both circuits test normal, test or replace the actuator.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Air Inlet Valve Actuator Replacement (Left Hand Drive) Air Inlet Valve Actuator Replacement (Left Hand Drive)Air Inlet Valve Actuator Replacement (Right Hand Drive) Air Inlet Valve Actuator Replacement (Right Hand Drive)
* Mode Valve Actuator Replacement Mode Valve Actuator Replacement
* Temperature Valve Actuator Replacement - Left Side Temperature Valve Actuator Replacement - Left Side
* Temperature Valve Actuator Replacement - Right Side Temperature Valve Actuator Replacement - Right Side
* Control Module References Control Module References for the HVAC control module replacement, setup, and programming