AutoCodes – GMC – P2771 GMC

P2771 GMC Code - Four Wheel Drive Low Switch Circuit

Quick Answer

For vehicles equipped with an active transfer case, the four-wheel drive (4WD) low circuit consists of the Powertrain Control Module (PCM), a transfer case control module, and the circuit wiring. Common causes include Faulty Transfer Case Shift Control Switch, Transfer Case Shift Control Switch harness is open or shorted, Transfer Case Shift Control Switch circuit poor electrical connection. 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 GMC indicates Four Wheel Drive Low Switch Circuit.
Common causes: Common causes include Faulty Transfer Case Shift Control Switch, Transfer Case Shift Control Switch harness is open or shorted, Transfer Case Shift Control Switch circuit poor electrical connection.
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.

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Code Popularity 5,028

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Sep 22, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P2771 GMC Description

For vehicles equipped with an active transfer case, the four-wheel drive (4WD) low circuit consists of the Powertrain Control Module (PCM), a transfer case control module, and the circuit wiring. The transfer case control module controls the 4WD low signal on the low signal circuit. When the operator selects 4WD low, the transfer case control module grounds the signal circuit, and the 4WD low signal voltage on the circuit changes from ignition voltage to zero volts. The PCM then compensates for transfer case gear reduction in the transmission output shaft speed (OSS) sensor signal. The PCM uses the transmission OSS sensor signal to adjust shift points, line pressure, and torque converter clutch (TCC) scheduling.
For vehicles not equipped with an active transfer case, the 4WD low circuit consists of the PCM, a transfer case switch, and the circuit wiring. The transfer case switch controls the 4WD low signal on the signal circuit. When the operator selects 4WD low, the transfer case switch closes, and the 4WD low signal voltage on the signal circuit changes from ignition voltage to zero volts. The PCM then compensates for transfer case gear reduction in the transmission output shaft speed (OSS) sensor signal. The PCM uses the transmission OSS sensor signal to adjust shift points, line pressure, and TCC scheduling.

OBDII Code P2771 GMC - Four Wheel Drive Low Switch Circuit - AutoCodes.com — P2771 GMC Code - Four Wheel Drive Low Switch Circuit

What does this mean?

What are the Possible Causes of the DTC P2771 GMC?

Faulty Transfer Case Shift Control Switch
Transfer Case Shift Control Switch harness is open or shorted
Transfer Case Shift Control Switch circuit poor electrical connection

How to Fix the DTC P2771 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 P2771 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

P2771 2014 GMC Sierra — Four Wheel Drive Low Switch Circuit
P2771 2015 GMC Sierra — Four Wheel Drive Low Switch Circuit
P2771 2016 GMC Sierra — Four Wheel Drive Low Switch Circuit
P2771 2017 GMC Sierra — Four Wheel Drive Low Switch Circuit
P2771 2018 GMC Sierra — Four Wheel Drive Low Switch Circuit

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 GMC Code

1. What are the common symptoms of OBDII code P2771 in a GMC vehicle?

The common symptoms of OBDII code P2771 in a GMC vehicle include issues with engaging or disengaging the four-wheel-drive system, erratic shifting behavior, and an illuminated check engine light.

2. What are the possible causes of OBDII code P2771 in a GMC vehicle?

Possible causes of OBDII code P2771 in a GMC vehicle can include a faulty four-wheel-drive low switch, damaged wiring or connectors in the circuit, a malfunctioning transfer case control module, or a software issue.

3. How can I diagnose the Four Wheel Drive Low Switch Circuit issue related to OBDII code P2771 in my GMC vehicle?

Diagnosing the Four Wheel Drive Low Switch Circuit issue related to OBDII code P2771 in your GMC vehicle involves inspecting the wiring and connectors for any damage, testing the functionality of the four-wheel-drive low switch, and using a scan tool to check for communication errors with the transfer case control module.

4. Is it safe to continue driving my GMC vehicle with OBDII code P2771 present?

It is not recommended to continue driving your GMC vehicle with OBDII code P2771 present, as it can lead to further damage to the four-wheel-drive system and potentially compromise the vehicle's drivability and safety.

5. Can I repair OBDII code P2771 in my GMC vehicle myself?

Repairing OBDII code P2771 in your GMC vehicle may require specialized knowledge and tools. It is recommended to consult a professional mechanic or dealership for proper diagnosis and repair of the Four Wheel Drive Low Switch Circuit issue.

6. Are there any common DIY fixes for resolving OBDII code P2771 in a GMC vehicle?

Common DIY fixes for resolving OBDII code P2771 in a GMC vehicle may include checking and cleaning the connectors and wiring related to the four-wheel-drive low switch, as well as ensuring proper alignment and engagement of the switch.

7. How much does it typically cost to repair OBDII code P2771 in a GMC vehicle?

The cost to repair OBDII code P2771 in a GMC vehicle can vary depending on the root cause of the issue, parts needed for replacement, and labor costs. It is advisable to obtain a few quotes from different mechanics or dealerships for an accurate estimate.

8. Can a faulty transfer case control module trigger OBDII code P2771 in a GMC vehicle?

Yes, a faulty transfer case control module can contribute to triggering OBDII code P2771 in a GMC vehicle, as it plays a crucial role in managing the four-wheel-drive system and communicating with the low switch circuit.

9. Will resetting the OBDII code P2771 clear the issue in my GMC vehicle?

Resetting the OBDII code P2771 may temporarily clear the check engine light, but it will not fix the underlying problem causing the Four Wheel Drive Low Switch Circuit issue. It is essential to address the root cause of the code for a lasting solution.

10. How can I prevent OBDII code P2771 from recurring in my GMC vehicle?

To prevent OBDII code P2771 from recurring in your GMC vehicle, it is essential to perform regular maintenance checks on the four-wheel-drive system, address any wiring or connector issues promptly, and follow the manufacturer's recommended service intervals.