AutoCodes – Toyota – U1104 Toyota

U1104 Toyota 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 Toyota 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 2,590

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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

What does this mean?

What are the Possible Causes of the DTC U1104 Toyota?

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 Toyota?

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 Toyota 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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Information for Specific Toyota Models

U1104 2013 Toyota RAV4 — Lost Communication with Driving Support ECU
U1104 2014 Toyota RAV4 — Lost Communication with Driving Support ECU
U1104 2015 Toyota RAV4 — Lost Communication with Driving Support ECU
U1104 2016 Toyota RAV4 — Lost Communication with Driving Support ECU
U1104 2017 Toyota RAV4 — Lost Communication with Driving Support ECU
U1104 2018 Toyota RAV4 — Lost Communication with Driving Support ECU

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.