AutoCodes – Cadillac – U0129 Cadillac

U0129 Cadillac 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 Cadillac 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 2,580

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

What does this mean?

What are the Possible Causes of the DTC U0129 Cadillac?

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 Cadillac?

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 Cadillac 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 Cadillac Code

What does OBDII code U0129 mean in a Cadillac?

OBDII code U0129 indicates a loss of communication with the Brake System Control Module, which can affect the vehicle's braking system and stability control features.

What are common symptoms of the U0129 code?

Common symptoms include the illumination of the ABS warning light, traction control light, or brake warning light, along with potential issues with braking performance or stability control features.

What can cause the U0129 code to trigger?

Causes may include a faulty Brake System Control Module, damaged wiring or connectors in the communication circuit, or issues with other related modules like the ABS module.

How can I diagnose the U0129 code?

Start by checking for other diagnostic trouble codes (DTCs) that might be present, inspect wiring and connectors for damage, and test the Brake System Control Module for proper operation.

Is it safe to drive my Cadillac with the U0129 code?

It is not recommended to drive the vehicle with this code, as it may impair braking performance and stability control, potentially leading to unsafe driving conditions.

What are some common repair tips for the U0129 code?

Repair tips include inspecting and repairing any damaged wiring or connectors, replacing the Brake System Control Module if faulty, and ensuring that all grounding points are clean and secure.

Can I reset the U0129 code without fixing the issue?

While you can clear the code with an OBDII scanner, the underlying issue must be resolved for the code to not return and for proper vehicle operation.

Will replacing the Brake System Control Module always fix the U0129 code?

Not necessarily; while a faulty module can cause the code, it's important to thoroughly diagnose the vehicle to rule out other causes such as wiring issues or problems with other modules.

How much does it typically cost to repair the U0129 code?

Repair costs can vary widely depending on the underlying issue, ranging from a simple wiring repair costing a few dollars to several hundred dollars if a module needs to be replaced.