B0418

DTC B0418

DTC DESCRIPTOR

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 B0428 61
Temperature Control 3 Circuit Actuator Stuck

DTC B0433 06
Temperature Control 3 Feedback Circuit Short to Ground or Open

DTC B3531 61
Air Flow Control 10 Circuit Actuator Stuck

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

DTC B3782 06
Air Flow Control 10 Feedback Circuit Short to Ground or Open

DIAGNOSTIC FAULT INFORMATION









IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection

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 control module supplies the actuator motor with a 12-volt control circuit and a ground control circuit. The HVAC module controls the direction of the actuator door by changing the polarity of the control circuits.

CONDITIONS FOR RUNNING THE DTC
- The ignition is on.
- Ignition voltage is between 9 and 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
Driver A and driver 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.
- The DTC can be cleared with a scan tool.

CIRCUIT/SYSTEM VERIFICATION
Ignition ON, command the appropriate actuator to 100% 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, test for less than 1.0 ohm of resistance between the low reference circuit and ground.
- If greater than 1.0 ohm, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
2. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit and ground.
- If less than 4.8 volts, 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 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
3. Verify the appropriate scan tool parameter is less than 4 counts.
- If greater than 4 counts, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the HVAC Control Module.
4. Install a 3-amp fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal. Verify the appropriate scan tool parameter is greater than 250 counts.
- If less than 250 counts, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
5. Ignition ON, after 30 seconds verify that a test lamp illuminates between control circuit A terminal and B+.
- If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal replace the HVAC control module.
6. Ignition OFF, verify that the test lamp does not illuminate between control circuit A terminal and B+.
- If the test lamp illuminate, test the control circuit for a short to ground. If circuit tests normal replace the HVAC control module.
7. Ignition ON, after 30 seconds verify that a test lamp illuminates between control circuit B terminal and B+.
- If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal replace the HVAC control module.
8. Ignition OFF, verify that the test lamp does not illuminate between control circuit B terminal and B+.
- If the test lamp illuminate, test the control circuit for a short to ground. If circuit tests normal replace the HVAC control module.
9. If all circuits test normal, replace the actuator.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

- HVAC Control Module Programming and Setup
- HVAC Control Module Programming and Setup - Auxiliary
- Recirculation Actuator Replacement
- Mode Actuator Replacement
- Air Temperature Actuator Replacement - Left
- Air Temperature Actuator Replacement - Right
- Air Temperature Actuator Replacement - Auxiliary
- Mode Actuator Replacement - Auxiliary.