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P2771 2018 GMC Sierra Code - Four Wheel Drive Low Switch Circuit

Quick Answer

The P2771 diagnostic trouble code (DTC) for a 2018 GMC Sierra relates to the Four Wheel Drive Low Switch Circuit. Common causes include Faulty Four Wheel Drive Low Switch, Damaged wiring or connectors in the circuit, Corrosion or poor connections in the circuit. 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
P2771 2018 GMC Sierra indicates Four Wheel Drive Low Switch Circuit.
Common causes
Common causes include Faulty Four Wheel Drive Low Switch, Damaged wiring or connectors in the circuit, Corrosion or poor connections in the circuit.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 17, 2024
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Code P2771 2018 GMC Sierra Description

The P2771 diagnostic trouble code (DTC) for a 2018 GMC Sierra relates to the Four Wheel Drive Low Switch Circuit. This code indicates that there is a malfunction in the circuit responsible for controlling the engagement of the four-wheel-drive low mode in the vehicle. The four-wheel-drive low mode is typically used for off-road driving or when towing heavy loads at low speeds. When this circuit malfunctions, it can prevent the vehicle from engaging or disengaging the four-wheel-drive low mode properly, affecting the vehicle's performance and drivability.

OBDII Code P2771 2018 GMC Sierra - Four Wheel Drive Low Switch Circuit
P2771 2018 GMC Sierra Code - Four Wheel Drive Low Switch Circuit

Common Causes of P2771 2018 GMC Sierra

  1. Faulty Four Wheel Drive Low Switch.
  2. Damaged wiring or connectors in the circuit.
  3. Corrosion or poor connections in the circuit.
  4. Issues with the control module that receives signals from the switch.
  5. Environmental factors such as water intrusion or debris affecting the components.

Symptoms of P2771 2018 GMC Sierra

  1. Difficulty engaging or disengaging four-wheel-drive low mode.
  2. Illumination of the four-wheel-drive warning light on the dashboard.
  3. Limited traction or stability in off-road or low-speed driving situations.
  4. Unusual noises coming from the transfer case when attempting to switch modes.
  5. Reduced fuel efficiency due to the system not operating optimally.

How to Fix P2771 2018 GMC Sierra

  1. Begin by diagnosing the specific cause of the P2771 code using a scan tool to pinpoint the exact issue.
  2. Inspect the Four Wheel Drive Low Switch and associated wiring for any visible damage or corrosion.
  3. Test the switch for proper functionality using a multimeter to check for continuity.
  4. Replace the faulty switch or repair any damaged wiring or connectors as needed.
  5. Clear the DTC from the vehicle's memory and test the system to ensure proper operation.

Cost to Fix P2771 2018 GMC Sierra

The typical repair costs for addressing the P2771 code on a 2018 GMC Sierra can range from $150 to $400, including parts and labor. However, it's important to note that actual costs can vary depending on the specific diagnosis time and labor rates at auto repair shops. Rates may be higher at dealerships or in metropolitan areas, while independent shops may offer more competitive prices. It's recommended to obtain quotes from local shops for a more accurate estimate.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P2771 2018 GMC Sierra Code

1. What does the OBDII code P2771 mean on a 2018 GMC Sierra?

P2771 indicates an issue with the Four-Wheel Drive Low (4LO) switch circuit, meaning the system is not detecting proper operation or communication from the 4LO switch.

2. What are the symptoms of code P2771 on a 2018 GMC Sierra?

Common symptoms include the inability to engage 4LO mode, a lit Check Engine Light, or a service 4WD warning on the dashboard.

3. What causes the P2771 code to appear on a 2018 GMC Sierra?

Possible causes include a faulty 4LO switch, damaged wiring or connectors in the switch circuit, a malfunctioning transfer case control module, or electrical issues such as a short or open circuit.

4. Can I drive my 2018 GMC Sierra with the P2771 code?

Yes, the vehicle can still be driven, but 4LO mode may not function, which could be problematic in off-road or towing situations requiring low-range gearing.

5. How is the P2771 code diagnosed?

A technician will use a scan tool to confirm the code, inspect the 4LO switch and its wiring for damage, test for proper voltage and continuity in the circuit, and check the transfer case control module.

6. How can I fix the P2771 code on my 2018 GMC Sierra?

Repairs may include replacing a faulty 4LO switch, repairing or replacing damaged wiring, cleaning corroded connectors, or reprogramming/replacing the transfer case control module if necessary.

7. How much does it cost to fix the P2771 code on a 2018 GMC Sierra?

Repair costs vary but typically range from $100 to $300 for a 4LO switch replacement, with higher costs if wiring repairs or module replacement are needed.

8. What tools are needed to repair the P2771 code?

Basic tools include a multimeter for electrical testing, a scan tool to confirm and clear the code, and possibly a replacement 4LO switch if needed.

9. Can I fix the P2771 code on my 2018 GMC Sierra myself?

If you have basic mechanical and electrical skills, you may be able to inspect and replace the 4LO switch or repair wiring. However, advanced diagnostic tools may be required for module issues.

10. Can a software update fix the P2771 code on a 2018 GMC Sierra?

In some cases, a software update for the transfer case control module may resolve the issue if the problem is related to a programming error rather than hardware failure.

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