P2771 2018 GMC Sierra 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 2018 GMC Sierra 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.
Code P2771 2018 GMC Sierra Description
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.
What are the Possible Causes of the DTC P2771 2018 GMC Sierra?
- 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 2018 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 P2771 2018 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 P2771 2018 GMC Sierra code?
Need more information on how to fix the P2771 2018 GMC Sierra code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P2771 2018 GMC Sierra code diagnosed by a professional: Find a repair shop in your area
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.
Discuss the causes and fixes for P2771 2018 GMC Sierra OBDII Code
Code P2771 2018 GMC Sierra comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
