AutoCodes – Lexus – U0129 Lexus

U0129 Lexus Code - Lost Communication with Brake System Control Module

Quick Answer

The Controller Area Network (CAN) is a standard bus system in vehicles that enables the connection of automotive devices without the need for a host computer. Common causes include Faulty Controller Area Network (CAN) Communication System, Faulty Brake System Control Module, Brake System Control Module harness is open or shorted. 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 Lexus indicates Lost Communication with Brake System Control Module.
Common causes: Common causes include Faulty Controller Area Network (CAN) Communication System, Faulty Brake System Control Module, Brake System Control Module harness is open or shorted.
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 2,074

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 Mar 26, 2023

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code U0129 Lexus Description

The Controller Area Network (CAN) is a standard bus system in vehicles that enables the connection of automotive devices without the need for a host computer. The exchange of operating information and commands among devices is facilitated by pre-programmed information about the required message exchange on the serial data circuits. Communication is carried out using two dedicated wires, known as CAN high and CAN low, with both lines carrying 2.5V when the CAN bus is in idle mode. During the transmission of data bits, the CAN high line increases to 3.75V while the CAN low drops to 1.25V, creating a 2.5V differential between the lines. Since communication relies on a voltage differential between the two bus lines, the CAN bus is NOT sensitive to inductive spikes, electrical fields, or other noise. The Diagnostic Trouble Code (DTC) sets when a periodic message from the Brake System Control Module has not been received.

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

What does this mean?

What are the Possible Causes of the DTC U0129 Lexus?

Faulty Controller Area Network (CAN) Communication System
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 Lexus?

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 does this mean?

Code Tech Notes

When there are problems with the way different systems in a vehicle communicate with each other using a technology called Controller Area Network (CAN) communication, Diagnostic Trouble Codes (DTC) are displayed. These codes can be caused by issues with the main bus or branch of the communication network, or with the Electronic Control Units (ECUs) and sensors that make up the different systems. If you see code for both the CAN communication problems and internal or power source problems at the same time, you should focus on fixing the internal or power source problems first.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U0129 Lexus 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 Lexus Code

1. What are the common symptoms of OBDII code U0129 in a Lexus related to a lost communication with the Brake System Control Module?

- Common symptoms include the ABS warning light or traction control light illuminating on the dashboard, loss of ABS functionality, and potential brake performance issues.

2. What are some possible causes of the U0129 code indicating a communication problem with the Brake System Control Module in a Lexus?

- Possible causes may include damaged wiring or connectors, a faulty Brake System Control Module, a software glitch, or a fault in the CAN bus communication system.

3. How can I diagnose the U0129 code in a Lexus indicating a lost communication with the Brake System Control Module?

- Proper diagnosis involves checking the wiring and connectors for any visible damage, testing the Brake System Control Module for functionality, and using a diagnostic tool to scan the vehicle's system for any stored fault codes.

4. What are some tips for repairing the U0129 code related to a lost communication with the Brake System Control Module in a Lexus?

- Repair tips may include repairing or replacing damaged wiring and connectors, reprogramming the Brake System Control Module if necessary, and ensuring proper communication within the vehicle's network.

5. Can I continue driving my Lexus with the U0129 code triggered due to a lost communication with the Brake System Control Module?

- It is not recommended to continue driving the vehicle with this code active, as it may lead to potential safety issues related to brake performance and ABS functionality.

6. How much does it typically cost to repair the U0129 code in a Lexus caused by a communication problem with the Brake System Control Module?

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

7. Is it possible to reset the U0129 code related to a lost communication with the Brake System Control Module in a Lexus without fixing the underlying issue?

- Resetting the code without addressing the underlying problem is not recommended, as the issue will persist and potentially lead to further complications with the vehicle's braking system.

8. How long does it typically take to repair the U0129 code in a Lexus due to a lost communication with the Brake System Control Module?

- The repair time can vary based on the specific cause of the communication problem, but it may take a few hours to a full day for diagnostics, repairs, and testing to be completed.

9. Are there any preventative measures to avoid triggering the U0129 code in a Lexus related to a lost communication with the Brake System Control Module?

- Regular maintenance checks, inspecting wiring for damage, and promptly addressing any warning lights related to the ABS system can help prevent issues leading to this code.

10. Can a DIY enthusiast with automotive experience repair the U0129 code indicating a communication problem with the Brake System Control Module in a Lexus?

- While some basic troubleshooting steps can be performed by DIY enthusiasts, diagnosing and repairing the specific cause of the U0129 code may require specialized tools and expertise best handled by a professional mechanic or technician.