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Engine-Codes – GMC – P279A 2018 GMC Sierra

P279A 2018 GMC Sierra Code - Four Wheel Drive High Range Performance

Quick Answer

The diagnostic trouble code P279A for a 2018 GMC Sierra relates to the Four Wheel Drive High Range Performance. Common causes include Faulty transfer case actuator, Malfunctioning transfer case control module, Wiring issues or loose connections in the four-wheel-drive system. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P279A 2018 GMC Sierra indicates Four Wheel Drive High Range Performance.
Common causes
Common causes include Faulty transfer case actuator, Malfunctioning transfer case control module, Wiring issues or loose connections in the four-wheel-drive system.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 14, 2024
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Code P279A 2018 GMC Sierra Description

The diagnostic trouble code P279A for a 2018 GMC Sierra relates to the Four Wheel Drive High Range Performance. This code indicates that there is a problem with the performance of the four-wheel-drive system when operating in high range mode. The high range mode is typically used for driving at higher speeds on normal road conditions. When this code is triggered, it can affect the vehicle's ability to engage or disengage the four-wheel-drive system properly, leading to issues with traction and stability.

OBDII Code P279A 2018 GMC Sierra - Four Wheel Drive High Range Performance
P279A 2018 GMC Sierra Code - Four Wheel Drive High Range Performance

Common Causes of P279A 2018 GMC Sierra

  1. Faulty transfer case actuator.
  2. Malfunctioning transfer case control module.
  3. Wiring issues or loose connections in the four-wheel-drive system.
  4. Sensor failure, such as the speed sensor or position sensor.
  5. Software glitches in the vehicle's control modules.

Symptoms of P279A 2018 GMC Sierra

  1. Difficulty engaging or disengaging four-wheel drive high range mode.
  2. Illumination of the four-wheel-drive warning light on the dashboard.
  3. Unusual noises coming from the transfer case or drivetrain.
  4. Reduced traction or stability when driving in high range mode.
  5. Decreased fuel efficiency due to the system not operating optimally.

How to Fix P279A 2018 GMC Sierra

  1. Begin by conducting a thorough diagnostic scan to confirm the P279A code and identify the specific cause of the issue.
  2. Inspect the transfer case actuator and control module for any signs of damage or malfunction.
  3. Check the wiring and connections in the four-wheel-drive system for any loose or damaged components.
  4. Test the sensors related to the four-wheel-drive system to ensure they are functioning correctly.
  5. If necessary, reprogram the vehicle's control modules to address any software glitches causing the code to be triggered.

Cost to Fix P279A 2018 GMC Sierra

The cost of repairing the Four Wheel Drive High Range Performance issue can vary depending on the specific cause of the problem. On average, the repair costs for this type of issue can range from $200 to $800, including parts and labor. However, it's important to note that diagnostic time and labor rates at auto repair shops can vary based on location, vehicle make and model, and engine type. It's recommended to check with local auto repair shops for a more accurate estimate based on your specific circumstances.

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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 P279A 2018 GMC Sierra Code

1. What does the OBDII code P279A mean on a 2018 GMC Sierra?

P279A indicates an issue with the Four-Wheel Drive (4WD) High Range Performance, which means the system is not functioning as expected in 4WD high mode.

2. What are the common symptoms of code P279A on a 2018 GMC Sierra?

Symptoms may include the 4WD system not engaging properly, illumination of the Check Engine Light or Service 4WD light, and reduced off-road or traction performance.

3. What causes the P279A code on a GMC Sierra?

Potential causes include a malfunctioning transfer case motor, damaged wiring or connectors in the 4WD system, a faulty transfer case control module, or mechanical issues within the transfer case itself.

4. Can driving with the P279A code damage my GMC Sierra?

Driving with this code may not immediately harm the vehicle, but it can lead to reduced traction in challenging conditions and potential long-term damage to the 4WD system if left unresolved.

5. How is the P279A code diagnosed?

A technician typically uses a scan tool to read the code, inspects the transfer case motor and wiring, checks for mechanical wear in the transfer case, and tests the transfer case control module for faults.

6. How can I fix the P279A code on my 2018 GMC Sierra?

Repairs may include replacing the transfer case motor, repairing or replacing damaged wiring or connectors, updating or replacing the transfer case control module, or addressing mechanical damage in the transfer case.

7. Is the P279A code covered under warranty for a 2018 GMC Sierra?

Coverage depends on your warranty terms. If your vehicle is still under a powertrain or drivetrain warranty, it may cover repairs related to the 4WD system.

8. Can low transfer case fluid cause the P279A code?

Yes, low or contaminated transfer case fluid can cause mechanical issues, which may trigger the P279A code. Checking and replacing the fluid is a good first step.

9. How much does it cost to repair the P279A code on a GMC Sierra?

Repair costs can vary depending on the exact issue but may range from $200 for minor repairs like wiring fixes to $1,500 or more for replacing the transfer case motor or control module.

10. Can I fix the P279A code myself?

If you're experienced with automotive repairs, you may be able to inspect and replace components like the transfer case motor or fluid. However, diagnosing electrical or control module issues may require professional tools and expertise.

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