P279B 2015 GMC Sierra Code - Four Wheel Drive Low 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
- P279B 2015 GMC Sierra indicates Four Wheel Drive Low 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.
Code P279B 2015 GMC Sierra Description
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.
What are the Possible Causes of the DTC P279B 2015 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 P279B 2015 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 P279B 2015 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.
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Frequently Asked Questions about P279B 2015 GMC Sierra Code
1. What does OBDII code P279B mean on a 2015 GMC Sierra?
Code P279B indicates an issue with the Four Wheel Drive (4WD) Low Range performance, which means the transfer case or related components are not functioning as expected in low range mode.
2. What are the common symptoms of code P279B on a 2015 GMC Sierra?
Symptoms may include the 4WD system not engaging in low range, a warning light or message on the dashboard, reduced off-road performance, or unusual noises from the transfer case.
3. What can cause the P279B code to appear on my GMC Sierra?
Common causes include a malfunctioning transfer case motor, faulty 4WD control module, wiring or connector issues, low or contaminated transfer case fluid, or mechanical damage in the transfer case.
4. Can driving with code P279B damage my 2015 GMC Sierra?
While driving in 2WD mode may not immediately damage the vehicle, attempting to use the 4WD system, especially in low range, could lead to further damage to the transfer case or drivetrain components.
5. How do I diagnose the P279B code on my GMC Sierra?
Diagnosis typically involves scanning for related codes, inspecting the transfer case motor and wiring, checking the transfer case fluid level and condition, and testing the 4WD system operation.
6. How can I fix the P279B code on my 2015 GMC Sierra?
Repairs may include replacing the transfer case motor, repairing damaged wiring, updating the 4WD control module software, or addressing mechanical issues in the transfer case.
7. Is the P279B code specific to the 2015 GMC Sierra?
No, the P279B code can appear on other vehicles with 4WD systems, but the exact causes and repairs may vary depending on the make and model.
8. How much does it cost to repair a P279B code on a 2015 GMC Sierra?
Repair costs range from $150 to $1,500 depending on the root cause, such as replacing a transfer case motor, repairing wiring, or addressing internal transfer case issues.
9. Can low transfer case fluid cause the P279B code?
Yes, low or contaminated transfer case fluid can affect the performance of the 4WD system and cause the P279B code to trigger.
10. Do I need a professional mechanic to fix the P279B code on my GMC Sierra?
While some issues like checking fluid levels or inspecting wiring can be done by experienced DIYers, diagnosing and repairing transfer case or electrical system problems often requires a professional mechanic.
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