AutoCodes – GMC – U18C8 2016 GMC Sierra

U18C8 2016 GMC Sierra Code - Glow Plug Control Module Lost Communication with Engine Control Module

Quick Answer

Devices connected to the 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: U18C8 2016 GMC Sierra indicates Glow Plug Control Module Lost Communication with Engine Control Module.
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 183

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 U18C8 2016 GMC Sierra Description

Devices connected to the 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 U18C8 2016 GMC Sierra - Glow Plug Control Module Lost Communication with Engine Control Module - AutoCodes.com — U18C8 2016 GMC Sierra Code - Glow Plug Control Module Lost Communication with Engine Control Module

What does this mean?

What are the Possible Causes of the DTC U18C8 2016 GMC Sierra?

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

How to Fix the DTC U18C8 2016 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 U18C8 2016 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 U18C8 2016 GMC Sierra code?

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Need Help with the 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 U18C8 2016 GMC Sierra Code

1. What are the common symptoms of OBDII code U18C8 in a 2016 GMC Sierra related to Glow Plug Control Module communication loss with the Engine Control Module?

- Common symptoms include rough idling, difficulty starting the vehicle, reduced engine performance, and the illumination of the Check Engine Light.

2. What are the possible causes of the U18C8 OBDII code in a 2016 GMC Sierra?

- The code U18C8 can be triggered by issues such as a faulty glow plug control module, damaged wiring or connectors, a defective engine control module, or communication network problems.

3. How can I diagnose the U18C8 code in my 2016 GMC Sierra?

- Proper diagnosis involves using an OBDII scanner to retrieve the code, inspecting the wiring and connectors for any damage, testing the glow plug control module, and checking the communication network between modules.

4. Can I continue driving my 2016 GMC Sierra with the U18C8 code present?

- It is not recommended to continue driving with the U18C8 code active, as it can lead to reduced engine performance and potential further damage if left unresolved.

5. How can I repair the U18C8 code in my 2016 GMC Sierra?

- Repairing the U18C8 code may involve replacing the glow plug control module, repairing or replacing damaged wiring or connectors, reprogramming modules if necessary, and ensuring proper communication between modules.

6. Is it possible to reset the U18C8 OBDII code in a 2016 GMC Sierra without fixing the underlying issue?

- While clearing the code with an OBDII scanner may temporarily turn off the Check Engine Light, the code is likely to return if the root cause is not addressed.

7. How much does it typically cost to repair the U18C8 code in a 2016 GMC Sierra?

- The cost of repairing the U18C8 code can vary depending on the specific cause of the issue, but it may range from around $200 to $500 for parts and labor.

8. Are there any preventive maintenance steps to avoid the U18C8 code in a 2016 GMC Sierra?

- Regularly inspecting the glow plug system, ensuring proper maintenance of electrical connections, and promptly addressing any warning signs can help prevent issues leading to the U18C8 code.

9. Can a DIY enthusiast fix the U18C8 code issue in a 2016 GMC Sierra?

- While some basic diagnosis and repairs like checking fuses or connectors can be done by a DIY enthusiast, diagnosing and fixing complex issues related to the U18C8 code may require professional expertise and specialized tools.

10. Will the U18C8 code affect the fuel efficiency of my 2016 GMC Sierra?

- Yes, the U18C8 code can potentially impact the fuel efficiency of your vehicle due to the compromised engine performance and incomplete combustion caused by glow plug system malfunctions.