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Engine-Codes – GMC – P279B GMC

P279B GMC Code - Four Wheel Drive Low Range Performance

Quick Answer

The P279B GMC code refers to Four Wheel Drive Low Range Performance. Common causes include Faulty sensors or switches related to the four-wheel-drive system, Malfunctioning transfer case, Damaged wiring or connectors 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
P279B GMC indicates Four Wheel Drive Low Range Performance .
Common causes
Common causes include Faulty sensors or switches related to the four-wheel-drive system, Malfunctioning transfer case, Damaged wiring or connectors 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 09, 2024
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Code P279B GMC Description

The P279B GMC code refers to Four Wheel Drive Low Range Performance. This code indicates that there is a performance issue with the low range function of the four-wheel-drive system in the vehicle. In vehicles equipped with four-wheel drive, the low range mode is used for increased torque and better traction when driving at low speeds, such as off-roading or towing heavy loads. When this code is triggered, it can affect the vehicle's ability to properly engage or disengage the low range mode, resulting in reduced performance, decreased traction, and potential drivability issues.

OBDII Code P279B GMC - Four Wheel Drive Low Range Performance
P279B GMC Code - Four Wheel Drive Low Range Performance

Common Causes of P279B GMC

  1. Faulty sensors or switches related to the four-wheel-drive system.
  2. Malfunctioning transfer case.
  3. Damaged wiring or connectors in the four-wheel-drive system.
  4. Problematic control module managing the low range function.
  5. Low fluid levels in the transfer case or differential.

Symptoms of P279B GMC

  1. Difficulty engaging or disengaging the four-wheel-drive low range mode.
  2. Unusual noises or vibrations when switching to low range.
  3. Decreased traction or performance when driving off-road or in challenging conditions.
  4. Dashboard warning lights related to the four-wheel-drive system.
  5. Limited power or acceleration in low range mode.

How to Fix P279B GMC

  1. Diagnose the specific cause of the code using a scan tool to retrieve additional fault codes and perform a visual inspection of the four-wheel-drive components.
  2. Check the fluid levels in the transfer case and differentials, topping up or replacing as necessary.
  3. Test the sensors, switches, and wiring associated with the four-wheel-drive system for proper functionality.
  4. Inspect the transfer case for any internal damage or wear, repair or replace components as needed.
  5. Reset the code and perform a test drive to ensure the issue has been resolved.

Cost to Fix P279B GMC

The cost of repairing the P279B GMC code can vary depending on the specific cause of the issue and the extent of the repairs needed. In general, the typical repair costs for this issue can range from $200 to $800, including parts and labor. However, it is essential to note that diagnosis time and labor rates at auto repair shops can vary based on factors such as location, vehicle make and model, and engine type. It is advisable to check with local auto repair shops for a more accurate estimate of the repair costs for this specific issue.

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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 P279B GMC Code

1. What does the OBDII code P279B mean on a GMC vehicle?

The P279B code indicates an issue with the Four-Wheel Drive (4WD) Low Range Performance, meaning the transfer case may not be engaging or functioning properly in low range mode.

2. What are the common symptoms of the P279B code?

Common symptoms include the 4WD warning light illuminating, inability to engage low range mode, reduced off-road performance, or unusual noises from the transfer case.

3. What causes the P279B code to appear on a GMC vehicle?

Possible 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 driving with the P279B code damage my GMC?

While you can typically drive in 2WD or high-range 4WD, ignoring the issue may worsen transfer case or drivetrain damage over time if not addressed.

5. How do I diagnose the P279B code on my GMC?

Start by checking the transfer case wiring and connectors for damage or corrosion, inspecting the shift motor, and using a diagnostic scanner to monitor the transfer case control module's performance.

6. How do I fix the P279B code on a GMC vehicle?

Repairs may include replacing the transfer case shift motor, repairing damaged wiring, reprogramming or replacing the transfer case control module, or addressing internal transfer case issues.

7. Is the transfer case shift motor often the cause of the P279B code?

Yes, a malfunctioning transfer case shift motor is a common cause, as it may fail to properly engage low range mode.

8. Can low transfer case fluid cause the P279B code?

Yes, low or contaminated transfer case fluid can lead to poor performance and trigger the P279B code.

9. How much does it cost to repair the P279B code on a GMC?

Repair costs vary but typically range from $200 to $1,500, depending on whether the issue is with the shift motor, wiring, or transfer case.

10. Can I clear the P279B code without fixing the issue?

You can clear the code with a diagnostic scanner, but it will likely return if the underlying problem isn’t resolved.

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