AutoCodes – GMC – U1129 GMC

U1129 GMC Code - Lost Communications With Audio Amplifier

Quick Answer

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Common causes include Faulty Audio Amplifier, Audio Amplifier harness is open or shorted, Audio Amplifier 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: U1129 GMC indicates Lost Communications With Audio Amplifier.
Common causes: Common causes include Faulty Audio Amplifier, Audio Amplifier harness is open or shorted, Audio Amplifier 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 521

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 22, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1129 GMC Description

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for the state of health monitoring/node alive messages. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once an identification number is learned by a module, it will monitor for that module node alive message. Each module on the class 2 serial data circuit is required to send a Node Alive message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a Diagnostic Trouble Code (DTC) U1129 is set.

OBDII Code U1129 GMC - Lost Communications With Audio Amplifier - AutoCodes.com — U1129 GMC Code - Lost Communications With Audio Amplifier

What does this mean?

What are the Possible Causes of the DTC U1129 GMC?

Faulty Audio Amplifier
Audio Amplifier harness is open or shorted
Audio Amplifier circuit poor electrical connection

How to Fix the DTC U1129 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 U1129 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 U1129 GMC Code

1. What are common symptoms of OBDII code U1129 GMC (Lost Communications With Audio Amplifier)?

- Common symptoms include loss of sound from the audio system, malfunctioning audio controls, and warning lights on the dashboard.

2. What are possible causes of OBDII code U1129 GMC?

- Possible causes include a faulty audio amplifier, damaged wiring or connectors, a blown fuse, or a problem with the communication network.

3. How can I diagnose the issue related to OBDII code U1129 GMC?

- Diagnose the issue by checking the audio amplifier for power and ground, inspecting the wiring harness for any damage, and using a scan tool to check for communication errors.

4. Can a blown fuse cause OBDII code U1129 GMC to appear?

- Yes, a blown fuse related to the audio system can trigger the U1129 code due to a loss of power to the audio amplifier.

5. How can I repair OBDII code U1129 GMC on my GMC vehicle?

- Repair the U1129 code by checking and replacing any blown fuses, repairing damaged wiring or connectors, and replacing the audio amplifier if necessary.

6. Is it safe to continue driving with OBDII code U1129 GMC present?

- It is generally safe to drive with the U1129 code, but it is recommended to address the issue promptly to restore proper functionality to the audio system.

7. Can a DIY enthusiast fix OBDII code U1129 GMC at home?

- Depending on the underlying cause, a DIY enthusiast may be able to fix the U1129 code at home by following repair guides and using basic tools.

8. Will resetting the OBDII code U1129 GMC make the issue go away permanently?

- Resetting the code may temporarily clear the warning, but if the root cause is not addressed, the code is likely to reappear.

9. How long does it typically take to repair OBDII code U1129 GMC?

- The repair time for the U1129 code can vary depending on the cause, but it can usually be fixed within a few hours to a day.

10. Is OBDII code U1129 GMC a common issue in GMC vehicles?

- The U1129 code related to lost communication with the audio amplifier is seen in some GMC vehicles, particularly in models with complex audio systems.