AutoCodes – GMC – B0408 2015 GMC Sierra

B0408 2015 GMC Sierra Code - Main Temperature Control Circuit

Quick Answer

Stepper motors are used for temperature regulation, air distribution control and recirculation door control. Common causes include Faulty Air Temperature Actuator, Air Temperature Actuator harness is open or shorted, Air Temperature Actuator circuit poor electrical connection. Severity is Low - monitor the vehicle and repair when practical. The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

What it means: B0408 2015 GMC Sierra indicates Main Temperature Control Circuit.
Common causes: Common causes include Faulty Air Temperature Actuator, Air Temperature Actuator harness is open or shorted, Air Temperature Actuator circuit poor electrical connection.
Severity: Low - monitor the vehicle and repair when practical.
Can I drive?: The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

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Code Popularity 259

How popular is this code, among other codes? Low

Repair Importance Level

Low (Monitor) (1 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 29, 2024

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code B0408 2015 GMC Sierra 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.

OBDII Code B0408 2015 GMC Sierra - Main Temperature Control Circuit - AutoCodes.com — B0408 2015 GMC Sierra Code - Main Temperature Control Circuit

What does this mean?

What are the Possible Causes of the DTC B0408 2015 GMC Sierra?

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 DTC B0408 2015 GMC Sierra?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code 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?

Labor: 1.0

To diagnose the B0408 2015 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the B0408 2015 GMC Sierra code?

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about B0408 2015 GMC Sierra Code

1. What is OBDII code B0408 for a 2015 GMC Sierra?

Code B0408 indicates a problem with the Main Temperature Control Circuit in the vehicle's HVAC system.

2. What are common symptoms of OBDII code B0408 in a 2015 GMC Sierra?

Common symptoms of code B0408 may include inconsistent temperature control in the cabin, hot air blowing when set to cool, or cold air blowing when set to heat.

3. What are some possible causes of OBDII code B0408 in a 2015 GMC Sierra?

Potential causes of code B0408 include a faulty main temperature control actuator, wiring issues, a malfunctioning control module, or a problem with the HVAC system's sensors.

4. How can I diagnose OBDII code B0408 in my 2015 GMC Sierra?

Diagnosing code B0408 may involve using a scan tool to retrieve the code, checking the main temperature control actuator for proper operation, inspecting the wiring for damage, and testing the control module and sensors.

5. Can I still drive my 2015 GMC Sierra with OBDII code B0408?

While the vehicle may still be operable with code B0408 present, it is recommended to address the issue promptly to ensure proper HVAC functionality and comfort.

6. How can I repair OBDII code B0408 in my 2015 GMC Sierra?

Repairing code B0408 may involve replacing the main temperature control actuator, repairing any damaged wiring, resetting the control module, or addressing any other identified issues in the HVAC system.

7. Are there any DIY tips for fixing OBDII code B0408 in a 2015 GMC Sierra?

DIY tips for addressing code B0408 may include checking and securing wiring connections, ensuring the actuator is properly installed, and following a service manual or online guides for step-by-step instructions.

8. Will resetting the OBDII code B0408 in my 2015 GMC Sierra make it go away permanently?

Resetting the code may clear it temporarily, but if the underlying issue causing code B0408 is not addressed, the code is likely to reappear once the problem resurfaces.

9. Can a faulty cabin air filter trigger OBDII code B0408 in a 2015 GMC Sierra?

While a clogged or dirty cabin air filter can affect HVAC performance, it is unlikely to directly trigger code B0408. It's best to focus on diagnosing the specific components related to the Main Temperature Control Circuit.

10. Is it necessary to visit a dealership for repairs related to OBDII code B0408 in a 2015 GMC Sierra?

While a dealership may have specialized knowledge and tools for GMC vehicles, independent repair shops or experienced DIYers can also address code B0408 as long as they have the necessary skills and equipment.