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U1104 Toyota Code - Lost Communication with Driving Support ECU

Quick Answer

The U1104 diagnostic trouble code (DTC) for Toyota 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 Loose or corroded wiring connections between the vehicle's main computer system and the Driving Support ECU, Faulty Driving Support ECU that is not sending or receiving signals properly, Software issues or glitches in the vehicle's computer system that are affecting communication. 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 Toyota indicates Lost Communication with Driving Support ECU.
Common causes
Common causes include Loose or corroded wiring connections between the vehicle's main computer system and the Driving Support ECU, Faulty Driving Support ECU that is not sending or receiving signals properly, Software issues or glitches in the vehicle's computer system that are affecting communication.
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 16, 2024
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Code U1104 Toyota Description

The U1104 diagnostic trouble code (DTC) for Toyota 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 assistance features such as lane departure warning, adaptive cruise control, and collision avoidance systems. When communication is lost with this ECU, it can lead to a loss of functionality in these driving support systems.

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

Common Causes of U1104 Toyota

  1. Loose or corroded wiring connections between the vehicle's main computer system and the Driving Support ECU.
  2. Faulty Driving Support ECU that is not sending or receiving signals properly.
  3. Software issues or glitches in the vehicle's computer system that are affecting communication.
  4. Electrical interference from other components or systems in the vehicle.
  5. Physical damage to wiring harnesses or connectors that are disrupting communication signals.

Symptoms of U1104 Toyota

  1. Malfunction indicator light (MIL) or check engine light illuminated on the dashboard.
  2. Loss of functionality in driving assistance features such as lane departure warning or adaptive cruise control.
  3. Erratic behavior or unresponsiveness of the vehicle's safety systems.
  4. Difficulty engaging or disengaging certain driving support features.
  5. Diagnostic trouble codes related to communication errors stored in the vehicle's computer system.

How to Fix U1104 Toyota

  1. Begin by conducting a thorough visual inspection of wiring connections and harnesses to check for any obvious signs of damage or corrosion.
  2. Use a diagnostic scan tool to retrieve and analyze the specific DTCs related to the communication issue with the Driving Support ECU.
  3. Test the functionality of the Driving Support ECU to determine if it is sending and receiving signals correctly.
  4. Check for software updates or reprogramming that may be necessary to resolve communication errors.
  5. Repair or replace any damaged wiring, connectors, or components that are impeding communication between the vehicle's systems.

Cost to Fix U1104 Toyota

The typical repair costs for addressing a U1104 code in a Toyota vehicle can vary depending on the specific cause of the communication issue. In general, parts and labor for this type of repair could range from $200 to $500 or more. It's important to note that diagnostic time and labor rates at auto repair shops can vary significantly, with hourly rates typically ranging from $80 to $150. Rates may be higher at dealerships or in metropolitan areas, while independent shops may offer more competitive pricing. For a more accurate estimate, it is recommended to consult with a local auto repair shop.

What does this mean?

Tech Notes for U1104 Toyota

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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Information for Specific Toyota Models

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 Toyota Code

1. What are the common symptoms of OBDII code U1104 in a Toyota vehicle?

- Common symptoms include the check engine light being illuminated, loss of communication with driving support systems, and potential issues with vehicle performance.

2. What does the OBDII code U1104 "Lost Communication with Driving Support ECU" mean in a Toyota?

- This code indicates a communication failure between the vehicle's onboard diagnostic system and the Driving Support Electronic Control Unit (ECU), which manages various driving support functions.

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

- The code U1104 can be triggered by issues such as damaged wiring or connectors, a faulty Driving Support ECU, software glitches, or a malfunctioning CAN bus communication network.

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

- Diagnosing this code typically involves checking the wiring and connectors related to the Driving Support ECU, verifying the ECU's functionality, and using a scan tool to analyze communication data on the CAN bus network.

5. Can I still drive my Toyota with the OBDII code U1104 present?

- It is generally not recommended to drive the vehicle with this code present, as it may affect the proper operation of driving support systems and potentially compromise safety.

6. How can I repair OBDII code U1104 in my Toyota?

- Repairing this code usually involves addressing the root cause, such as repairing damaged wiring, replacing faulty connectors or the Driving Support ECU, and ensuring proper communication on the CAN bus network.

7. Is it possible to reset OBDII code U1104 in a Toyota without fixing the underlying issue?

- While clearing the code may temporarily turn off the check engine light, it is crucial to address the underlying problem causing the communication error to prevent future issues and ensure proper vehicle operation.

8. Can a DIY enthusiast fix OBDII code U1104 in a Toyota?

- Depending on the specific cause of the code, some DIY enthusiasts with automotive repair experience may be able to diagnose and fix issues related to U1104, such as checking wiring connections or replacing components.

9. How much does it typically cost to repair OBDII code U1104 in a Toyota at a dealership or repair shop?

- Repair costs for U1104 can vary depending on the underlying issue, but expect to pay for diagnostic time, parts replacement, and labor costs, which can range from a couple of hundred to over a thousand dollars.

10. Are there any preventive measures to avoid OBDII code U1104 in a Toyota?

- Regular maintenance, including checking wiring integrity, ensuring proper connections, and promptly addressing any related warning signs, can help prevent issues leading to the U1104 code in a Toyota.

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