AutoCodes – Lexus – U1104 Lexus

U1104 Lexus Code - Lost Communication with Driving Support ECU

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 Driving Support ECU, Driving Support ECU 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: U1104 Lexus indicates Lost Communication with Driving Support ECU.
Common causes: Common causes include Faulty Controller Area Network (CAN) Communication System, Faulty Driving Support ECU, Driving Support ECU 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 1,056

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 27, 2023

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code U1104 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 Driving Support ECU has not been received.

OBDII Code U1104 Lexus - Lost Communication with Driving Support ECU - AutoCodes.com — U1104 Lexus Code - Lost Communication with Driving Support ECU

What does this mean?

What are the Possible Causes of the DTC U1104 Lexus?

Faulty Controller Area Network (CAN) Communication System
Faulty Driving Support ECU
Driving Support ECU harness is open or shorted
Driving Support ECU circuit poor electrical connection

How to Fix the DTC U1104 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 U1104 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 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.