P279B 2017 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 2017 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 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 P279B 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 P279B 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 P279B 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.
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Frequently Asked Questions about P279B 2017 GMC Sierra Code
1. What does the OBDII code P279B mean on a 2017 GMC Sierra?
P279B indicates an issue with the Four-Wheel Drive (4WD) Low Range Performance, typically related to the transfer case or associated components.
2. What are common symptoms of code P279B in a 2017 GMC Sierra?
Common symptoms include the inability to shift into 4WD Low, a "Service 4WD" message on the dashboard, and potential reduced off-road performance.
3. What causes the P279B code in a 2017 GMC Sierra?
Possible causes include a malfunctioning transfer case control module, a faulty transfer case motor, damaged wiring or connectors, or low or contaminated transfer case fluid.
4. Can I drive my 2017 GMC Sierra with the P279B code active?
While the truck may still be drivable, you may lose access to 4WD Low functionality, which could limit off-road or towing capabilities.
5. How do I diagnose the P279B code on a 2017 GMC Sierra?
Diagnosis involves scanning for additional codes, visually inspecting wiring and connectors, testing the transfer case motor, and checking the transfer case fluid level and condition.
6. What repairs might fix the P279B code on a 2017 GMC Sierra?
Repairs could include replacing the transfer case motor, repairing wiring or connectors, updating or reprogramming the transfer case control module, or changing the transfer case fluid.
7. How much does it cost to fix code P279B on a 2017 GMC Sierra?
Repair costs vary, but replacing a transfer case motor might range from $300 to $700, while addressing wiring or module issues could vary widely depending on labor.
8. Can low or dirty transfer case fluid cause the P279B code?
Yes, low or contaminated transfer case fluid can impair the system's performance and trigger the P279B code.
9. Is a software update needed to resolve the P279B code on a 2017 GMC Sierra?
In some cases, the transfer case control module may need a software update to resolve the issue, but a mechanic will need to confirm this through diagnosis.
10. What tools are required to troubleshoot the P279B code on a 2017 GMC Sierra?
You’ll need an OBDII scanner, a multimeter for electrical tests, and basic tools to inspect the transfer case motor and wiring.
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