P279B 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 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 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?
- 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?
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 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 Makes
- P279B Buick — Four Wheel Drive Low Range Performance
- P279B Cadillac — Four Wheel Drive Low Range Performance
- P279B Chevrolet — Four Wheel Drive Low Range Performance
- P279B GMC — Four Wheel Drive Low Range Performance
Frequently Asked Questions about P279B Code
1. What does the OBDII code P279B mean?
The P279B code indicates an issue with the "Four Wheel Drive Low Range Performance," suggesting that the performance of the four-wheel drive (4WD) system in low-range mode is outside the expected parameters set by the manufacturer.
2. What are common symptoms of the P279B code?
Symptoms may include the 4WD system failing to engage or disengage properly, unusual noises when switching to low range, and the 4WD light blinking or remaining illuminated. The vehicle might also show a decrease in traction or performance in off-road or tough driving conditions.
3. What can cause the P279B code to appear?
Possible causes include faulty four-wheel drive actuators or solenoids, damaged mechanical components in the transfer case, issues with the electronic control module, or wiring and sensor problems related to the 4WD system.
4. How can I diagnose the P279B code?
Diagnosis should start with reading all stored codes using an OBDII scanner, followed by a thorough visual inspection of the 4WD system components, including wiring and connectors. Testing the functionality of the 4WD actuators and solenoids, as well as checking for mechanical issues in the transfer case, is also crucial.
5. What are the steps to fix the P279B code?
Repair steps might include replacing faulty 4WD actuators or solenoids, repairing or replacing damaged wiring or connectors, and addressing any mechanical faults within the transfer case. In some cases, reprogramming or replacing the 4WD system’s electronic control module may be necessary.
6. Is it safe to drive with the P279B code?
While you may be able to drive the vehicle, doing so with a malfunctioning 4WD system could lead to further damage or reduced vehicle control, especially in adverse conditions. It's advisable to address the issue promptly to ensure optimal vehicle performance and safety.
7. Can the P279B code affect the fuel economy of the vehicle?
Yes, if the 4WD system is stuck in low range mode, it could lead to increased fuel consumption. Additionally, mechanical drag or resistance due to a malfunctioning 4WD system can also negatively impact fuel efficiency.
8. What tools are needed to diagnose and repair issues related to the P279B code?
Tools needed may include an OBDII scanner, multimeter for electrical tests, and mechanical tools for accessing and repairing the 4WD system components. A professional-grade scanner might be required for deeper diagnostics or to reprogram the control modules.
9. How often do issues leading to the P279B code occur in vehicles?
The frequency of issues related to the P279B code can vary based on the make and model of the vehicle, usage patterns, and the quality of maintenance performed. Regular maintenance and timely repairs are crucial to minimizing the occurrence of such issues.
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