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U1104 Lexus Code - Lost Communication with Driving Support ECU

Quick Answer

The U1104 diagnostic trouble code (DTC) for Lexus vehicles indicates that there is a communication problem between the vehicle's onboard computer system and the Driving Support Electronic Control Unit (ECU). Common causes include Faulty wiring or connectors in the communication network, Corrosion or damage to the communication bus lines, Software glitches or programming errors in the vehicle's computer system. 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
U1104 Lexus indicates Lost Communication with Driving Support ECU.
Common causes
Common causes include Faulty wiring or connectors in the communication network, Corrosion or damage to the communication bus lines, Software glitches or programming errors in the vehicle's computer system.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 13, 2024
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Code U1104 Lexus Description

The U1104 diagnostic trouble code (DTC) for Lexus vehicles indicates that there is a communication problem between the vehicle's onboard computer system and the Driving Support Electronic Control Unit (ECU). The Driving Support ECU is responsible for managing various driving support systems, such as adaptive cruise control, lane departure warning, and collision avoidance systems. When communication is lost with this ECU, it can lead to the malfunction or complete shutdown of these important safety features.

OBDII Code U1104 Lexus - Lost Communication with Driving Support ECU
U1104 Lexus Code - Lost Communication with Driving Support ECU

Common Causes of U1104 Lexus

  1. Faulty wiring or connectors in the communication network
  2. Corrosion or damage to the communication bus lines
  3. Software glitches or programming errors in the vehicle's computer system
  4. Faulty Driving Support ECU
  5. Electrical interference from aftermarket accessories or modifications

Symptoms of U1104 Lexus

  1. Malfunction or complete failure of adaptive cruise control system
  2. Inoperative lane departure warning system
  3. Disabled collision avoidance system
  4. Illumination of the check engine light
  5. Loss of communication with other vehicle control modules

How to Fix U1104 Lexus

  1. Begin by conducting a thorough inspection of the vehicle's wiring harness and connectors to check for any visible damage or corrosion. Repair or replace any damaged components.
  2. Use a diagnostic scan tool to communicate with the vehicle's computer system and identify the specific communication error codes. Clear any stored codes and reattempt communication with the Driving Support ECU.
  3. Check for software updates or reprogramming procedures provided by the manufacturer to address known communication issues.
  4. If the issue persists, consider replacing the Driving Support ECU with a new or remanufactured unit. Ensure that the replacement unit is properly programmed and calibrated to work with the vehicle's specific make and model.
  5. After completing the repair process, perform a thorough test drive to verify that the driving support systems are functioning correctly and that the U1104 code does not return.

Cost to Fix U1104 Lexus

The typical repair costs for addressing a U1104 code on a Lexus vehicle can vary depending on the specific cause of the communication issue and the extent of the repairs needed. In general, replacing faulty wiring or connectors may cost between $100 and $300, while replacing the Driving Support ECU can range from $500 to $1500, including parts and labor. Additional diagnostic fees and labor costs may apply, with total repair costs potentially exceeding $2000 in some cases. It's important to consult with a qualified mechanic or dealership to obtain an accurate cost estimate based on the vehicle's make and model, as well as the local labor rates in your area.

What does this mean?

Tech Notes for U1104 Lexus

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.

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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 U1104 Lexus Code

1. What does the OBDII code U1104 for Lexus mean?

The U1104 code indicates a communication issue with the Driving Support Electronic Control Unit (ECU) in a Lexus vehicle.

2. What are the common symptoms of U1104 code in a Lexus?

Common symptoms of the U1104 code include loss of communication with driving support systems like adaptive cruise control, lane departure warning, or collision avoidance features.

3. What are the possible causes of the U1104 code in a Lexus?

Possible causes of the U1104 code include wiring issues, loose connections, a faulty driving support ECU, a software glitch, or a malfunction in the communication network.

4. How can I diagnose the U1104 code in my Lexus?

Diagnosing the U1104 code involves checking the wiring and connections related to the driving support ECU, scanning for other related trouble codes, and using a professional diagnostic tool to communicate with the ECU.

5. Is it safe to drive with the U1104 code present in a Lexus?

It is not recommended to drive with the U1104 code present, as it may affect the operation of critical driving support systems in your Lexus.

6. How can I repair the U1104 code in my Lexus?

Repairing the U1104 code may involve fixing any wiring or connection issues, ensuring the driving support ECU is functioning correctly, updating software if needed, and clearing the trouble code with a diagnostic tool.

7. Can a DIY enthusiast fix the U1104 code in a Lexus?

While some basic checks like inspecting connections can be done by a DIY enthusiast, diagnosing and repairing the U1104 code may require advanced diagnostic tools and expertise, best left to professional technicians.

8. How much does it cost to repair the U1104 code in a Lexus?

The cost of repairing the U1104 code can vary depending on the specific cause of the issue, parts needed for replacement, and labor costs at a repair shop. It is advisable to get a few quotes from different mechanics.

9. Will resetting the U1104 code make it go away permanently?

Resetting the U1104 code may temporarily clear the trouble code, but if the underlying issue causing the communication problem is not fixed, the code is likely to return.

10. Can the U1104 code be related to other problems in a Lexus?

The U1104 code is specifically related to a loss of communication with the driving support ECU, but it may be connected to other issues affecting the vehicle's electronic systems or sensors.

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