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Engine-Codes – GMC – P279C 2018 GMC Sierra

P279C 2018 GMC Sierra Code - Four Wheel Drive Neutral Range Performance

Quick Answer

The P279C diagnostic trouble code for a 2018 GMC Sierra indicates an issue with the Four Wheel Drive Neutral Range Performance. Common causes include Faulty four-wheel-drive actuator, Wiring issues or electrical faults in the four-wheel-drive system, Malfunctioning transfer case control module. 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
P279C 2018 GMC Sierra indicates Four Wheel Drive Neutral Range Performance.
Common causes
Common causes include Faulty four-wheel-drive actuator, Wiring issues or electrical faults in the four-wheel-drive system, Malfunctioning transfer case control module.
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 Aug 18, 2024
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Code P279C 2018 GMC Sierra Description

The P279C diagnostic trouble code for a 2018 GMC Sierra indicates an issue with the Four Wheel Drive Neutral Range Performance. This means that the vehicle's four-wheel-drive system is not functioning properly, specifically in the neutral range. The neutral range is an important setting that allows the vehicle to be towed without causing damage to the drivetrain. When this code is triggered, it can affect the vehicle's ability to switch between two-wheel drive and four-wheel drive modes, potentially leading to drivability issues and safety concerns.

OBDII Code P279C 2018 GMC Sierra - Four Wheel Drive Neutral Range Performance
P279C 2018 GMC Sierra Code - Four Wheel Drive Neutral Range Performance

Common Causes of P279C 2018 GMC Sierra

  1. Faulty four-wheel-drive actuator
  2. Wiring issues or electrical faults in the four-wheel-drive system
  3. Malfunctioning transfer case control module
  4. Mechanical issues in the transfer case or drivetrain components
  5. Low fluid levels or contaminated fluid in the transfer case

Symptoms of P279C 2018 GMC Sierra

  1. Difficulty engaging or disengaging four-wheel drive mode
  2. Strange noises or vibrations when switching between drive modes
  3. Dashboard warning lights related to the four-wheel-drive system
  4. Reduced traction or stability on slippery surfaces
  5. Inability to shift into neutral range for towing purposes

How to Fix P279C 2018 GMC Sierra

  1. Diagnose the specific cause of the issue using a professional diagnostic tool
  2. Inspect the four-wheel-drive actuator and wiring for any signs of damage or wear
  3. Test the transfer case control module for proper function and replace if necessary
  4. Check and refill transfer case fluid levels with the manufacturer-recommended fluid
  5. Clear the diagnostic trouble code from the vehicle's computer system and test the four-wheel-drive system for proper operation

Cost to Fix P279C 2018 GMC Sierra

The cost of repairing a Four Wheel Drive Neutral Range Performance issue can vary depending on the specific cause of the problem and the labor rates in your area. On average, you can expect to pay anywhere from $200 to $800 for parts and labor. Keep in mind that additional costs may apply if any components need to be replaced or if further diagnostics are required. It's recommended to consult with a trusted mechanic or dealership for a more accurate estimate based on your vehicle's make and model.

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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 P279C 2018 GMC Sierra Code

1. What does the OBDII code P279C indicate on a 2018 GMC Sierra?

The P279C code on a 2018 GMC Sierra indicates an issue with the "Four Wheel Drive Neutral Range Performance," suggesting a malfunction in the transfer case's ability to switch into or out of neutral.

2. What are the common symptoms of code P279C in a 2018 GMC Sierra?

Common symptoms include the inability to switch the four-wheel drive system into or out of neutral, unusual noises from under the vehicle, the 4WD light blinking or remaining on, and possibly the vehicle failing to engage or disengage four-wheel drive mode.

3. What causes the P279C code to appear on my 2018 GMC Sierra?

Potential causes for the P279C code include a faulty four-wheel drive switch, damaged wiring or connectors in the four-wheel drive system, a defective transfer case actuator, or issues with the transfer case control module.

4. How can I diagnose the P279C code on my 2018 GMC Sierra?

Diagnosis involves using a scan tool to read the fault code and inspecting the four-wheel drive system components such as the switch, wiring, and actuator. Checking for additional diagnostic trouble codes can also help pinpoint the specific malfunction.

5. What are the repair steps for fixing code P279C on a 2018 GMC Sierra?

Repair steps typically include checking and replacing the four-wheel drive switch if faulty, repairing or replacing damaged wiring or connectors, replacing a faulty transfer case actuator, or reprogramming or replacing the transfer case control module if necessary.

6. Is it safe to drive my 2018 GMC Sierra with the P279C code active?

While you might still be able to drive your vehicle, it's advised to address the issue promptly as it affects the performance of the four-wheel drive system, which can be crucial in certain driving conditions and might lead to further damage if ignored.

7. Can a P279C code affect the fuel economy of my 2018 GMC Sierra?

Yes, if the four-wheel drive system is stuck in one mode due to this issue, it could potentially affect the fuel economy by causing the vehicle to operate less efficiently than designed.

8. What tools are necessary to diagnose the P279C code on a 2018 GMC Sierra?

Essential tools include a professional-grade scan tool capable of reading and clearing codes, as well as accessing real-time data from the four-wheel drive system, and basic hand tools for inspecting and repairing physical components like switches and actuators.

9. How long does it typically take to fix the P279C code on a 2018 GMC Sierra?

The repair time can vary based on the specific cause of the code, ranging from an hour for simple switch replacements to several hours for more complex issues such as wiring repairs or actuator replacements.

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