Engine-Codes.com
Engine-Codes – GMC – B1390 2018 GMC Sierra

B1390 2018 GMC Sierra Code - Control Module Supply Circuit 1

Quick Answer

The B1390 diagnostic trouble code (DTC) for a 2018 GMC Sierra refers to an issue with the Control Module Supply Circuit 1. Common causes include Faulty control module power supply relay, Wiring or connector issues in the control module supply circuit, Battery or alternator problems affecting voltage supply. 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
B1390 2018 GMC Sierra indicates Control Module Supply Circuit 1.
Common causes
Common causes include Faulty control module power supply relay, Wiring or connector issues in the control module supply circuit, Battery or alternator problems affecting voltage supply.
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 08, 2024
💬 Need more help? Ask Auto Expert for instant answers — it's free!
AutoCodes App

Fix Your Car Smarter

Try the New AutoCodes App!

Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.

AutoCodes App on Google Play

Code B1390 2018 GMC Sierra Description

The B1390 diagnostic trouble code (DTC) for a 2018 GMC Sierra refers to an issue with the Control Module Supply Circuit 1. In modern vehicles, control modules are responsible for managing various systems and functions, such as engine performance, transmission operation, emissions control, and more. The control module supply circuit provides power to these modules, ensuring they can operate effectively. When this circuit has a fault, it can lead to significant issues with the vehicle's performance and overall functionality.

OBDII Code B1390 2018 GMC Sierra - Control Module Supply Circuit 1
B1390 2018 GMC Sierra Code - Control Module Supply Circuit 1

Common Causes of B1390 2018 GMC Sierra

  1. Faulty control module power supply relay.
  2. Wiring or connector issues in the control module supply circuit.
  3. Battery or alternator problems affecting voltage supply.
  4. Defective control module itself.
  5. Corrosion or damage to the control module supply circuit components.

Symptoms of B1390 2018 GMC Sierra

  1. Warning lights on the dashboard, such as the Check Engine Light or other system-specific indicators.
  2. Loss of power or reduced engine performance.
  3. Rough idling or irregular engine behavior.
  4. Transmission issues, such as erratic shifting or hesitation.
  5. In severe cases, the vehicle may fail to start or exhibit starting difficulties.

How to Fix B1390 2018 GMC Sierra

  1. Begin by performing a thorough inspection of the control module supply circuit, checking for any visible damage to wiring or connectors.
  2. Test the control module power supply relay to ensure it is functioning correctly. Replace if necessary.
  3. Verify the voltage output from the battery and alternator to ensure they are within the specified range for the control module.
  4. If no issues are found with the above steps, the control module itself may need to be replaced.
  5. Clear the diagnostic trouble codes from the vehicle's system and test to ensure the issue has been resolved.

Cost to Fix B1390 2018 GMC Sierra

The typical repair costs for addressing a B1390 code on a 2018 GMC Sierra can vary depending on the specific cause of the issue and the parts/labour required for the repair. On average, the cost for parts and labour may range from $200 to $500. However, it is important to note that diagnosis time and labour rates at auto repair shops can vary significantly. Rates in metropolitan areas or at dealerships may be higher, while independent shops may offer lower prices. It is advisable to obtain quotes from multiple sources to get a more accurate estimate for the repair.

Need more information about the B1390 2018 GMC Sierra code?

Need more information on how to fix the B1390 2018 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B1390 2018 GMC Sierra code diagnosed by a professional: Find a repair shop in your area

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 B1390 2018 GMC Sierra Code

1. What does the OBDII code B1390 mean on a 2018 GMC Sierra?

The code B1390 indicates an issue with the "Control Module Supply Circuit 1," which refers to a problem with the power supply to a control module in the vehicle.

2. What are the common symptoms of code B1390 on a 2018 GMC Sierra?

Symptoms may include warning lights on the dashboard, malfunctioning electrical components, communication errors between modules, or the vehicle failing to start.

3. What causes the B1390 code to appear on a 2018 GMC Sierra?

Common causes include a blown fuse, faulty wiring, a damaged control module, corroded or loose electrical connections, or a failing power supply relay.

4. How do I diagnose the B1390 code on my GMC Sierra?

Start by inspecting fuses, checking the wiring for damage or corrosion, and testing the control module’s power and ground connections. Use a multimeter and a scan tool to assist with testing.

5. Can I drive my 2018 GMC Sierra with a B1390 code?

It’s not recommended to drive with this code active, as it may lead to further electrical issues or loss of functionality in critical vehicle systems.

6. How do I fix the B1390 code on a 2018 GMC Sierra?

Repairs may include replacing a blown fuse, repairing damaged wiring, cleaning and tightening electrical connections, or replacing a faulty control module or power supply relay.

7. How much does it cost to repair the B1390 code on a 2018 GMC Sierra?

Repair costs can vary widely based on the root cause, ranging from $50 for a simple fuse replacement to $500 or more for module or wiring repairs.

8. Can a weak battery cause the B1390 code on a 2018 GMC Sierra?

Yes, a weak or failing battery can cause insufficient voltage supply to the control module, triggering the B1390 code.

9. Do I need to reprogram the control module after fixing a B1390 code?

In some cases, if the control module is replaced, reprogramming or reinitialization may be required using a GM-specific scan tool.

10. What tools are needed to troubleshoot the B1390 code on a 2018 GMC Sierra?

You’ll typically need a digital multimeter, a scan tool with GM compatibility, and wiring diagrams specific to the 2018 GMC Sierra.

Discuss the causes and fixes for B1390 2018 GMC Sierra OBDII Code

Submit a New Comment

Code B1390 2018 GMC Sierra comments

No comments found for this page.