AutoCodes – GMC – U1818 2018 GMC Sierra

U1818 2018 GMC Sierra Code - Lost Communication with Engine Control Module on Powertrain Expansion Communication Bus

Quick Answer

Devices connected to the powertrain high-speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Engine Control Module (ECM), Engine Control Module harness is open or shorted, Engine Control Module 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: U1818 2018 GMC Sierra indicates Lost Communication with Engine Control Module on Powertrain Expansion Communication Bus.
Common causes: Common causes include Faulty Engine Control Module (ECM), Engine Control Module harness is open or shorted, Engine Control Module 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 217

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 24, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1818 2018 GMC Sierra Description

Devices connected to the powertrain high-speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices. The devices have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver device as an availability indication of the transmitter device. Each message contains the identification number of the transmitter device.
The Diagnostic Trouble Code (DTC) will be set when a supervised periodic message that includes the transmitter device availability has not been received.

OBDII Code U1818 2018 GMC Sierra - Lost Communication with Engine Control Module on Powertrain Expansion Communication Bus - AutoCodes.com — U1818 2018 GMC Sierra Code - Lost Communication with Engine Control Module on Powertrain Expansion Communication Bus

What does this mean?

What are the Possible Causes of the DTC U1818 2018 GMC Sierra?

Faulty Engine Control Module (ECM)
Engine Control Module harness is open or shorted
Engine Control Module circuit poor electrical connection

How to Fix the DTC U1818 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 U1818 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 U1818 2018 GMC Sierra code?

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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 U1818 2018 GMC Sierra Code

1. What does the OBDII code U1818 mean on a 2018 GMC Sierra?

The code U1818 signifies a communication issue where the Engine Control Module (ECM) has lost communication on the Powertrain Expansion Communication Bus.

2. What are common symptoms of the U1818 code on a 2018 GMC Sierra?

Common symptoms include the check engine light illuminating, engine stalling or misfiring, reduced fuel efficiency, and potential difficulty starting the vehicle.

3. What are possible causes of the U1818 code on a 2018 GMC Sierra?

Potential causes of the U1818 code include a faulty ECM, wiring or connection issues in the communication bus, a malfunctioning powertrain control module, or a software glitch.

4. How can I diagnose the U1818 code on my 2018 GMC Sierra?

Diagnosing the U1818 code typically involves using a diagnostic scanner to retrieve the trouble codes, inspecting the wiring and connections in the communication bus, checking for any loose connections, and testing the ECM and other related components.

5. How do I repair the U1818 code on my 2018 GMC Sierra?

Repairing the U1818 code may involve repairing or replacing any damaged wiring or connections in the communication bus, resetting the ECM, updating software if necessary, or replacing the ECM or powertrain control module if deemed faulty.

6. Can I still drive my 2018 GMC Sierra with the U1818 code present?

It is not recommended to drive your vehicle with the U1818 code present, as it can lead to further damage and potential safety hazards. It is advisable to address the issue promptly.

7. How much does it cost to fix the U1818 code on a 2018 GMC Sierra?

The cost of fixing the U1818 code can vary depending on the underlying cause of the issue. Repairs may range from a simple wiring repair to replacing the ECM or powertrain control module, potentially costing several hundred to over a thousand dollars.

8. Are there any preventive measures to avoid the U1818 code on a 2018 GMC Sierra?

Regularly servicing and maintaining your vehicle, ensuring all connections are secure, and addressing any warning signs promptly can help prevent issues like the U1818 code from occurring.

9. Can a DIY enthusiast fix the U1818 code on a 2018 GMC Sierra?

While diagnosing and repairing the U1818 code may require some technical knowledge and tools, DIY enthusiasts with experience in automotive repairs may be able to address the issue themselves by following diagnostic guides and repair procedures.

10. How long does it take to fix the U1818 code on a 2018 GMC Sierra?

The time needed to fix the U1818 code can vary based on the complexity of the issue and the repair required. Simple fixes like resetting the ECM or repairing a connection may take a short time, while more involved repairs could take several hours or more.