HVAC System - Manual
DTC B0228, B0413, B0423, or B3779
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC B0228 02
- Recirculate Position Feedback Circuit Short to Ground (CJ3)
DTC B0228 05
- Recirculate Position Feedback Circuit Short to Battery or Open (CJ3)
DTC B0228 61
- Recirculate Position Circuit Actuator Stuck (CJ3)
DTC B0413 02
- Temperature Control 1 Feedback Circuit Short to Ground (CJ3)
DTC B0413 05
- Temperature Control 1 Feedback Circuit Short to Battery or Open (CJ3)
DTC B0413 61
- Temperature Control 1 Feedback Circuit Actuator Stuck Open (CJ3)
DTC B0423 02
- Temperature Control 2 Feedback Circuit Short to Ground (CJ3+C67)
DTC B0423 05
- Temperature Control 2 Feedback Circuit Short to Battery or Open (CJ3+C67)
DTC B0423 61
- Temperature Control 2 Circuit Actuator Stuck (CJ3+C67)
DTC B3779 02
- Air Flow Control 9 Feedback Circuit Short to Ground (CJ3)
DTC B3779 05
- Air Flow Control 9 Feedback Circuit Short to Battery or Open (CJ3)
DTC B3779 61
- Air Flow Control 9 Circuit Actuator Stuck (CJ3)
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 control circuit uses either a 0, 2.5 or 5-volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands the actuator movement in opposite directions.
B0228
This DTC is for the recirculate actuator.
B0413
This DTC is for the drivers air temperature actuator.
B0423
This DTC is for the passenger air temperature actuator.
B3779
This DTC is for the mode actuator.
Conditions for Running the DTC
* The ignition is 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 6 counts or greater than 250 counts.
Action Taken When the DTC Sets
The control circuit is 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.
* The DTC can be cleared with a scan tool.
Circuit/System Verification
Ignition ON, operate the applicable actuator using the HVAC controls. The applicable scan tool parameter should transition from 6 counts to 250 counts.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the applicable actuator.
2. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal 7 and ground.
• 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.
3. Ignition ON, test for 4.4-5.2 volts between the 5-volt reference circuit terminal 10 and ground.
• 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.
• If less then 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.
4. Verify the applicable scan tool parameter is less than 7 counts.
• If greater than the specified range, test the signal circuit terminal 9 for a short to ground. If the circuit tests normal, replace the HVAC control module.
5. Install a 3A fused jumper wire between the signal circuit terminal 9 and the low reference circuit terminal 7. Verify the applicable scan tool parameter is greater than 250 counts.
• If less 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.
6. Verify that a test lamp illuminates between the ignition circuit terminal 5 and ground.
• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
7. Test for 2.5 volts between the control circuit terminal 6 and ground.
• If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
• If less then 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.
8. Install a DMM between the control circuit terminal 6 and ground. Command the actuator in each direction. Voltage on the control circuit should change from 0 volts when commanding the actuator in one direction to 5 volts in the other direction and return to 2.5 volts in the at rest state.
• If the voltage does not change as specified, replace the HVAC control module.
9. If all circuits test normal, test or replace the applicable actuator.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Air Temperature Actuator Replacement - Right Side
* Air Temperature Actuator Replacement - Left Side
* Mode Actuator Replacement
* Recirculation Actuator Replacement