B0408 on Buick
Temperature Control (Air Mix) Circuit Malfunction
B0408 on Buick vehicles indicates temperature control (air mix) circuit malfunction. Au7o has documented this code across 1 Buick model — most commonly on Enclave. B0408 is a body (B) code relating to the climate control system's temperature/air-mix control circuit. It generally means the HVAC module detected a fault in the circuit that controls the air-mix (blend) door, which regulates how much air is blended for the desired cabin temperature. Exact wording is somewhat manufacturer-specific, but it typically results in inability to control temperature on one or both sides. This is a comfort-system fault and not a safety or drivability hazard. Typical repair costs on Buick range from $200 to $600, depending on the specific model and root cause.
Common Causes of B0408
- •Failed air-mix (blend door) actuator/servo motor
- •Broken or jammed blend door
- •Wiring or connector fault in the actuator circuit
- •Loss of power or ground to the actuator
- •Faulty HVAC control module
- •Calibration/positioning fault after battery disconnect
B0408 on Buick by Model
Buick Enclave(1 issue)
- HVAC Blend Door Actuator Failure2008-2017
Enclaves commonly suffer failed HVAC blend-door actuators, with the plastic internal gears stripping or the small motor dying, often after about 80,000 miles. Because multiple actuators control temperature blend, vent direction, and recirculation, a failure leaves one zone stuck hot or cold, or produces a clicking/knocking sound behind the dash. The part itself is inexpensive but labor varies widely by which actuator failed.
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View B0408 across all makes →Frequently Asked Questions
What does B0408 mean on Buick?▼
B0408 stands for "Temperature Control (Air Mix) Circuit Malfunction." B0408 is a body (B) code relating to the climate control system's temperature/air-mix control circuit. It generally means the HVAC module detected a fault in the circuit that controls the air-mix (blend) door, which regulates how much air is blended for the desired cabin temperature. Exact wording is somewhat manufacturer-specific, but it typically results in inability to control temperature on one or both sides. This is a comfort-system fault and not a safety or drivability hazard. On Buick specifically, this code is documented across 1 model.
What causes B0408 on Buick vehicles?▼
Common causes on Buick: Failed air-mix (blend door) actuator/servo motor, Broken or jammed blend door, Wiring or connector fault in the actuator circuit, Loss of power or ground to the actuator, Faulty HVAC control module. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix B0408 on a Buick?▼
Repair costs on Buick range from $200 to $600, depending on the specific model and root cause.
Which Buick models have B0408 documented?▼
Au7o has documented B0408 on 1 Buick model: Enclave.