Engine-Codes - Generic - B0408

B0408 Code - Main Temperature Control Circuit

- Code Popularity: 2,842 Views
- Repair Importance Level: 1/3
- Repair Difficulty Level: 2/3
Table of contents

|What are the Possible Causes of the Code B0408?

  • 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

|How to Fix the B0408 Code?

Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

|Code B0408 Tech Notes

B0413:02 Main Temperature Control Circuit Short to Ground
B0413:05 Main Temperature Control Circuit Short to Battery or Open
B0413:61 Main Temperature Control Circuit Actuator Stuck Open

|What is the Cost to Diagnose the Code B0408?

Labor: 1.0

The cost to diagnose the B0408 code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.

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|What are Code B0408 Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

|What Does the B0408 Code Mean?

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.

Main Temperature Control Circuit

|Need more Information on the B0408 Code?

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|Code B0408 Information for Specific Makes

|Need Help with the B0408 Code?

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