P279A GMC Code - Four Wheel Drive High 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
- P279A GMC indicates Four Wheel Drive High 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 P279A GMC 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 P279A GMC?
- 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 P279A GMC?
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 P279A GMC 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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Information for Specific GMC Models
- P279A 2014 GMC Sierra — Four Wheel Drive High Range Performance
- P279A 2015 GMC Sierra — Four Wheel Drive High Range Performance
- P279A 2016 GMC Sierra — Four Wheel Drive High Range Performance
- P279A 2017 GMC Sierra — Four Wheel Drive High Range Performance
- P279A 2018 GMC Sierra — Four Wheel Drive High Range Performance
Frequently Asked Questions about P279A GMC Code
1. What are the common symptoms of OBDII code P279A GMC (Four Wheel Drive High Range Performance)?
- Common symptoms include difficulty engaging or disengaging four-wheel drive, erratic shifting between high and low range, and illumination of the four-wheel drive warning light.
2. What are some possible causes of OBDII code P279A GMC?
- Possible causes include a faulty four-wheel drive actuator, damaged wiring or connectors in the four-wheel drive system, or issues with the transfer case control module.
3. How can I diagnose the OBDII code P279A GMC?
- Diagnosing this code typically involves using a scan tool to retrieve the trouble codes, inspecting the four-wheel drive system components for any visible damage, and testing the functionality of the actuators and sensors.
4. Is it safe to continue driving with OBDII code P279A GMC active?
- It is not recommended to continue driving with this code active, as it can lead to potential drivability issues and further damage to the four-wheel drive system.
5. How can I repair OBDII code P279A GMC?
- Repairing this code may involve replacing the faulty four-wheel drive actuator, repairing any damaged wiring or connectors, or reprogramming the transfer case control module.
6. Can a DIYer fix OBDII code P279A GMC, or is it better left to professionals?
- While some basic diagnostic steps can be performed by a DIYer, resolving this code may require specialized tools and expertise, so it is recommended to consult a professional mechanic for accurate diagnosis and repair.
7. Are there any preventive maintenance tips to avoid OBDII code P279A GMC?
- Regularly inspecting and maintaining the four-wheel drive system components, such as keeping the actuators clean and well-lubricated, can help prevent issues that may trigger this fault code.
8. How long does it typically take to repair OBDII code P279A GMC?
- The repair time for this code can vary depending on the exact cause of the issue and the extent of repairs needed, but it may take a few hours to a day to diagnose and fix the problem.
9. Will resetting the OBDII code P279A GMC turn off the warning light?
- Resetting the code may temporarily turn off the warning light, but if the underlying issue is not fixed, the code is likely to reappear and illuminate the warning light again.
10. Can extreme weather conditions affect the occurrence of OBDII code P279A GMC?
- Yes, extreme weather conditions, such as very cold temperatures or heavy moisture, can sometimes exacerbate issues in the four-wheel drive system that may trigger this fault code.
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