AutoCodes – GMC – U0129 GMC

U0129 GMC Code - Lost Communication with Brake System Control Module

Quick Answer

Modules connected to the high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Brake System Control Module, Brake System Control Module harness is open or shorted, Brake System 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: U0129 GMC indicates Lost Communication with Brake System Control Module.
Common causes: Common causes include Faulty Brake System Control Module, Brake System Control Module harness is open or shorted, Brake System 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 1,331

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 Apr 01, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0129 GMC Description

Modules connected to the 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 modules. The modules 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 module as an availability indication of the transmitter module. The supervision time-out period is 250 ms. Each message contains the identification number of the transmitter module. The Diagnostic Trouble Code (DTC) sets when a periodic message from the Brake System Control Module has not been received.

OBDII Code U0129 GMC - Lost Communication with Brake System Control Module - AutoCodes.com — U0129 GMC Code - Lost Communication with Brake System Control Module

What does this mean?

What are the Possible Causes of the DTC U0129 GMC?

Faulty Brake System Control Module
Brake System Control Module harness is open or shorted
Brake System Control Module circuit poor electrical connection

How to Fix the DTC U0129 GMC?

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 U0129 GMC 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.

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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 U0129 GMC Code

1. What are common symptoms of the OBDII code U0129 GMC "Lost Communication with Brake System Control Module"?

- Common symptoms include the ABS warning light illuminated on the dashboard, loss of traction control functionality, and potential issues with the brake system.

2. What are the possible causes of the U0129 code in a GMC vehicle?

- The U0129 code can be caused by a faulty brake system control module, damaged wiring or connectors, a drained or faulty battery, or issues with the communication network.

3. How can I diagnose the U0129 code in my GMC vehicle?

- Diagnosing the U0129 code requires using an OBDII scanner to retrieve the code, checking for other related codes, inspecting the brake system control module and its connections, and testing the communication network.

4. Can I drive my GMC vehicle with the U0129 code present?

- It is not recommended to drive your GMC vehicle with the U0129 code present, as it can affect the proper functioning of the brake system and other safety features.

5. How can I repair the "Lost Communication with Brake System Control Module" issue?

- Repairing the U0129 code involves checking and repairing any damaged wiring or connectors, replacing the brake system control module if necessary, and ensuring proper communication between modules.

6. Is the U0129 code a serious issue in a GMC vehicle?

- Yes, the U0129 code is a serious issue as it indicates a loss of communication with the brake system control module, which can compromise the safety and performance of the vehicle.

7. Will resetting the trouble codes make the U0129 code disappear?

- Resetting the trouble codes may temporarily clear the U0129 code, but if the underlying issue causing the communication loss is not addressed, the code is likely to reappear.

8. Can a DIY enthusiast fix the U0129 code on a GMC vehicle?

- While some basic troubleshooting steps can be performed by a DIY enthusiast, diagnosing and repairing the U0129 code may require advanced tools and expertise, so professional help is recommended.

9. How much does it typically cost to repair the U0129 code in a GMC vehicle?

- The cost of repairing the U0129 code can vary depending on the underlying cause, but it may involve costs for diagnostic services, replacement parts, and labor, which can range from a few hundred to over a thousand dollars.

10. How can I prevent the U0129 code from reoccurring in the future?

- To prevent the U0129 code from reoccurring, it's essential to maintain the vehicle's electrical system, perform regular inspections, and address any related issues promptly to ensure proper communication between modules.