AutoCodes – GMC – P279C 2017 GMC Sierra

P279C 2017 GMC Sierra Code - Four Wheel Drive Neutral Range Performance

Quick Answer

The Engine Control Module (ECM) uses the following two ways to determine if the transfer case is in 4WD Low, 4WD High, or Neutral. Common causes include Reprogram Engine Control Module (ECM), Faulty Engine Control Module, Engine Control Module harness is open or shorted. 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 2017 GMC Sierra indicates Four Wheel Drive Neutral Range Performance.
Common causes: Common causes include Reprogram Engine Control Module (ECM), Faulty Engine Control Module, Engine Control Module harness is open or shorted.
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.

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Code Popularity 203

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Aug 29, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P279C 2017 GMC Sierra Description

The Engine Control Module (ECM) uses the following two ways to determine if the transfer case is in 4WD Low, 4WD High, or Neutral.
1. The first way is to compare the transmission output speed sensor to the transfer case output speed sensor in order to calculate the transfer case range.
2. The second way is to use a LAN message sent by the transfer case shift control module to the ECM.
The ECM uses this message to determine motor torque required and transmission shifting.
The internal fault detection is handled inside the control module. No external circuit diagnosis is involved.
If the first way and second way of determining transfer case range do not match while in 4WD Low, 4WD High or Neutral, then the Diagnostic Trouble Code (DTC) is set.

OBDII Code P279C 2017 GMC Sierra - Four Wheel Drive Neutral Range Performance - AutoCodes.com — P279C 2017 GMC Sierra Code - Four Wheel Drive Neutral Range Performance

What does this mean?

What are the Possible Causes of the DTC P279C 2017 GMC Sierra?

Reprogram Engine Control Module (ECM)
Faulty Engine Control Module
Engine Control Module harness is open or shorted
Engine Control Module circuit poor electrical connection
Transmission internal mechanical problems

How to Fix the DTC P279C 2017 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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P279C 2017 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 P279C 2017 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 P279C 2017 GMC Sierra Code

1. What does the OBDII code P279C mean on a 2017 GMC Sierra?

P279C indicates an issue with the Four-Wheel Drive Neutral Range Performance, meaning the transfer case is not shifting into or functioning correctly in neutral range.

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

Symptoms may include a check engine light, the four-wheel-drive system not engaging properly, difficulty shifting into neutral range, or unusual noises from the transfer case.

3. What causes the P279C code to appear on a 2017 GMC Sierra?

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 driving with the P279C code damage my GMC Sierra?

Yes, driving with this code can lead to further damage to the transfer case or drivetrain components if the issue is not resolved promptly.

5. How is the P279C code diagnosed on a GMC Sierra?

A technician will use a scan tool to check the code, inspect the transfer case and its components, test the shift motor, and check the wiring and connectors for damage or corrosion.

6. How do you fix the P279C code on a 2017 GMC Sierra?

Repairs might include replacing the transfer case shift motor, repairing or replacing damaged wiring, reprogramming or replacing the transfer case control module, or repairing internal transfer case components.

7. How much does it cost to fix the P279C code on a GMC Sierra?

Repair costs can vary widely depending on the specific issue, ranging from $200 for wiring repairs to $1,500 or more for transfer case replacement.

8. Can a P279C code be triggered by low fluid levels in the transfer case?

Yes, insufficient or contaminated transfer case fluid can cause performance issues and may trigger the P279C code.

9. Is the P279C code specific to GMC vehicles?

No, the P279C code can appear on other vehicles with a similar four-wheel-drive system, but the diagnosis and repair process may vary.

10. Can I reset the P279C code without repairing the issue?

Clearing the code with a scan tool may temporarily turn off the check engine light, but the issue will likely return until the root cause is addressed.