AutoCodes – GMC – U18C8 2014 GMC Sierra

U18C8 2014 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 2014 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 259

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 2014 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 2014 GMC Sierra - Glow Plug Control Module Lost Communication with Engine Control Module - AutoCodes.com — U18C8 2014 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 2014 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 2014 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 2014 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 2014 GMC Sierra code?

Need more information on how to fix the U18C8 2014 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U18C8 2014 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 U18C8 2014 GMC Sierra Code

1. What are the common symptoms of OBDII code U18C8 in a 2014 GMC Sierra?

The common symptoms of code U18C8 include issues with starting the engine, rough idling, decreased fuel efficiency, and potential loss of power.

2. What can cause the Glow Plug Control Module to lose communication with the Engine Control Module in a 2014 GMC Sierra?

Possible causes of this communication error can include damaged wiring or connectors, a faulty glow plug control module, a malfunctioning engine control module, or software issues.

3. How serious is the U18C8 trouble code in a 2014 GMC Sierra?

While the vehicle may still be operable with this code present, it is important to address the underlying communication issue promptly to prevent further complications and potential damage to the engine.

4. Can I continue driving my 2014 GMC Sierra with the U18C8 code active?

It is generally not recommended to drive the vehicle with an active U18C8 code, as it can lead to performance issues, reduced fuel efficiency, and potential long-term damage to engine components.

5. How can I diagnose and repair the U18C8 code in my 2014 GMC Sierra?

Diagnosing and repairing the U18C8 code typically involves checking the wiring and connectors for damage, testing the glow plug control module and engine control module, and addressing any software-related issues using diagnostic tools.

6. Is it possible to reset the U18C8 trouble code in a 2014 GMC Sierra without fixing the underlying issue?

While clearing the trouble code may temporarily turn off the warning light, it is essential to address the root cause of the communication error to prevent the code from reoccurring.

7. How much does it cost to repair the U18C8 code in a 2014 GMC Sierra?

The cost of repairing the U18C8 code can vary depending on the specific cause of the communication error, the labor rates of the repair shop, and the cost of any replacement parts that may be needed.

8. Can a DIY enthusiast fix the U18C8 trouble code in a 2014 GMC Sierra?

While some aspects of diagnosing and repairing the U18C8 code may be within reach of experienced DIY enthusiasts, it is recommended to consult a professional mechanic for accurate diagnosis and proper repair to ensure the issue is resolved effectively.

9. Will the U18C8 code cause my 2014 GMC Sierra to fail an emissions test?

Since the U18C8 code is related to communication between modules rather than emissions specifically, it may not directly cause the vehicle to fail an emissions test. However, it is still important to address the issue promptly for overall vehicle health.

10. How can I prevent the U18C8 trouble code from appearing again in my 2014 GMC Sierra?

Regular maintenance, such as checking and maintaining wiring connections, keeping the modules clean and free of debris, and addressing any potential issues promptly, can help prevent the recurrence of the U18C8 code in the future.