B0408 – Front Temperature Control Circuit

B0408 Possible Symptoms

Engine Light ON (or Service Engine Soon Warning Light)

B0408 Possible Causes

Faulty Air Temperature Actuator,Air Temperature Actuator harness is open or shorted,Air Temperature Actuator circuit poor electrical connection,Faulty Heating, Ventilation, and Air Conditioning (HVAC) Control Module

B0408 Description

Stepper motors are used for temperature regulation, air distribution control and recirculation door control. With the switches and dials on the HVAC controls, air temperature door position, mode door position and recirculation door position can be selected. The selected values are passed to the Heating, Ventilation, and Air Conditioning (HVAC) Control Module via serial data. The HVAC control module supplies a 12 V reference voltage to the stepper motors and energizes the 4 stepper motor coils with a pulsed ground signal. The stepper motors move the appropriate doors into the calculated positions, in order to reach the desired positions.