P279A 2017 GMC Sierra 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 2017 GMC Sierra 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 2017 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 P279A 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 P279A 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 P279A 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 P279A 2017 GMC Sierra code?
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Frequently Asked Questions about P279A 2017 GMC Sierra Code
1. What does OBDII code P279A mean on a 2017 GMC Sierra?
P279A indicates a "Four Wheel Drive High Range Performance" issue, meaning the vehicle's 4WD system is not performing as expected when in high-range mode.
2. What are common symptoms of code P279A in a 2017 GMC Sierra?
Symptoms include the 4WD system not engaging properly, warning lights on the dashboard like the "Service 4WD" light, reduced traction, or unusual noises from the drivetrain.
3. What causes the P279A code in a 2017 GMC Sierra?
Potential causes include a faulty transfer case motor, damaged wiring or connectors, a malfunctioning 4WD control module, or internal transfer case issues.
4. Can I drive my 2017 GMC Sierra with a P279A code?
While the vehicle may still be drivable in 2WD, it could compromise performance in off-road or slippery conditions. It's best to address the issue promptly.
5. How do I diagnose a P279A code on a 2017 GMC Sierra?
Start by scanning for codes using an OBDII scanner, inspecting the transfer case motor and its wiring, and testing the 4WD control module for proper operation.
6. Can a faulty transfer case motor cause the P279A code?
Yes, a malfunctioning transfer case motor is a common cause of this code, as it is responsible for shifting the vehicle into 4WD high-range mode.
7. How much does it cost to fix a P279A code on a 2017 GMC Sierra?
Repair costs vary but may range from $200 to $1,000 depending on whether the issue is with the transfer case motor, wiring, or other components.
8. Can I reset the P279A code without repairs?
Clearing the code with an OBDII scanner may temporarily remove the warning, but the underlying issue will likely cause the code to return.
9. Does the P279A code indicate a serious problem?
While not immediately dangerous, ignoring the code can lead to further damage to the 4WD system or transfer case, increasing repair costs.
10. What preventive maintenance can help avoid a P279A code?
Regularly inspect and maintain the transfer case, lubricate moving parts, and ensure the 4WD system is used periodically to prevent components from seizing.
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