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Engine-Codes – GMC – P279C GMC

P279C GMC Code - Four Wheel Drive Neutral Range Performance

Quick Answer

The P279C diagnostic trouble code (DTC) for GMC vehicles indicates a problem with the Four Wheel Drive (4WD) Neutral Range Performance. Common causes include Faulty 4WD actuator or motor, Malfunctioning 4WD control module, Wiring or electrical issues in the 4WD 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
P279C GMC indicates Four Wheel Drive Neutral Range Performance.
Common causes
Common causes include Faulty 4WD actuator or motor, Malfunctioning 4WD control module, Wiring or electrical issues in the 4WD 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 09, 2024
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Code P279C GMC Description

The P279C diagnostic trouble code (DTC) for GMC vehicles indicates a problem with the Four Wheel Drive (4WD) Neutral Range Performance. This code is typically seen in vehicles equipped with a 4WD system, where the neutral range refers to a state in which the vehicle's transmission is disengaged from the wheels, allowing the vehicle to be towed or moved without the drivetrain engaged.

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

Common Causes of P279C GMC

  1. Faulty 4WD actuator or motor
  2. Malfunctioning 4WD control module
  3. Wiring or electrical issues in the 4WD system
  4. Mechanical problems in the transfer case or transmission
  5. Low fluid levels or contaminated fluid in the 4WD system

Symptoms of P279C GMC

  1. Inability to engage or disengage 4WD mode
  2. Dashboard warning lights related to 4WD system
  3. Unusual noises coming from the 4WD system
  4. Poor traction or stability on slippery surfaces
  5. Difficulty towing the vehicle in neutral

How to Fix P279C GMC

  1. Diagnose the issue using a scan tool to determine the specific cause of the problem.
  2. Inspect the 4WD actuator, motor, and control module for any signs of damage or malfunction.
  3. Check the wiring and connectors in the 4WD system for any loose connections or corrosion.
  4. Test the transfer case and transmission for any mechanical issues that may be affecting the neutral range performance.
  5. Repair or replace any faulty components identified during the diagnostic process and clear the DTC from the vehicle's computer.

Cost to Fix P279C GMC

The cost of repairing the Four Wheel Drive Neutral Range Performance issue can vary depending on the specific cause of the problem and the extent of the repairs needed. On average, the repair costs for this issue can range from $200 to $800, including parts and labor. However, it's important to note that the actual cost may be higher or lower based on factors such as the vehicle's make and model, the location of the repair shop, and the complexity of the repairs required. It is recommended to obtain quotes from local auto repair shops to get a more accurate estimate for this repair.

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Information for Specific GMC Models

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 GMC Code

1. What does the OBDII code P279C mean on a GMC vehicle?

P279C indicates a "Four Wheel Drive Neutral Range Performance" issue, meaning the vehicle's transfer case system is not engaging or operating in the neutral range as expected.

2. What are common symptoms of the P279C code?

Symptoms may include the 4WD system not shifting into neutral, the service 4WD light illuminating, unusual noises from the transfer case, or the vehicle being stuck in a specific drive mode.

3. What causes the P279C code to be triggered?

Common causes include a faulty transfer case shift motor, damaged wiring or connectors, a malfunctioning transfer case control module, or mechanical issues within the transfer case.

4. Can I continue driving with the P279C code?

While the vehicle may still be drivable in some cases, ignoring this code can lead to further damage to the 4WD system. It’s best to address the issue promptly.

5. How is the P279C code diagnosed?

A technician will use a scan tool to verify the code, inspect the transfer case wiring and connectors, test the transfer case shift motor, and check for mechanical issues in the transfer case assembly.

6. How do I fix the P279C code on my GMC?

Repairs may involve replacing the transfer case shift motor, repairing damaged wiring or connectors, reprogramming or replacing the transfer case control module, or addressing internal transfer case damage.

7. Can a bad transfer case motor cause the P279C code?

Yes, a faulty transfer case shift motor is a common cause of this code as it prevents the system from shifting into the neutral range.

8. How much does it cost to fix the P279C code?

Repair costs can vary widely but may range from $300 to $1,500 depending on whether the issue is electrical (e.g., wiring or motor replacement) or mechanical (e.g., transfer case repair).

9. Can a software update fix the P279C code?

In some cases, a software update for the transfer case control module may resolve the code if it’s caused by a programming issue.

10. What tools are needed to diagnose the P279C code?

A professional-grade scan tool, a multimeter for testing electrical components, and potentially specialized tools for inspecting or disassembling the transfer case are needed for diagnosis.

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