B0408 on Cadillac
Temperature Control (Air Mix) Circuit Malfunction
B0408 on Cadillac vehicles indicates temperature control (air mix) circuit malfunction. Au7o has documented this code across 1 Cadillac model — most commonly on XTS. 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 Cadillac range from $120 to $450, 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 Cadillac by Model
Cadillac XTS(1 issue)
- HVAC Blend Door Actuator Clicking / Blower Resistor No Heat2013-2019
Two related HVAC complaints are common on the XTS: a repetitive clicking/knocking from behind the dash caused by a failing blend-door (temperature) actuator that can't reach its calibration stop, and loss of fan-speed control or no heat from a failed blower motor resistor/module — when the resistor fails the fan often works only on the highest setting. Owners report inconsistent temperature (one side hot/one cold) with the actuator fault and a dead or single-speed blower with the resistor fault.
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What does B0408 mean on Cadillac?▼
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 Cadillac specifically, this code is documented across 1 model.
What causes B0408 on Cadillac vehicles?▼
Common causes on Cadillac: 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 Cadillac?▼
Repair costs on Cadillac range from $120 to $450, depending on the specific model and root cause.
Which Cadillac models have B0408 documented?▼
Au7o has documented B0408 on 1 Cadillac model: XTS.