AutoCodes – Toyota – U1104 2018 Toyota RAV4

U1104 2018 Toyota RAV4 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 2018 Toyota RAV4 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 394

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 2018 Toyota RAV4 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 2018 Toyota RAV4 - Lost Communication with Driving Support ECU - AutoCodes.com — U1104 2018 Toyota RAV4 Code - Lost Communication with Driving Support ECU

What does this mean?

What are the Possible Causes of the DTC U1104 2018 Toyota RAV4?

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 2018 Toyota RAV4?

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 2018 Toyota RAV4 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 2018 Toyota RAV4 Code

1. What does the OBDII code U1104 mean on a 2018 Toyota RAV4?

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

2. What are the common symptoms of U1104 code in a 2018 Toyota RAV4?

Common symptoms include issues with the vehicle's driving support systems, such as malfunctioning adaptive cruise control or lane-keeping assist features.

3. What are the possible causes of the U1104 code in a 2018 Toyota RAV4?

Potential causes can include faulty wiring connections, a defective driving support ECU, software issues, or a communication network problem within the vehicle.

4. How can I diagnose the U1104 code on my 2018 Toyota RAV4?

Diagnosis typically involves using a professional OBDII scanner to retrieve the code, checking for other related codes, inspecting wiring connections, and performing communication tests with the affected ECU.

5. Can I still drive my 2018 Toyota RAV4 with the U1104 code present?

While the vehicle may still be drivable, it is advisable to address the issue promptly to prevent any potential safety hazards or further damage to the driving support systems.

6. How can I repair the U1104 code on my 2018 Toyota RAV4?

Repair methods may include checking and repairing wiring connections, replacing the driving support ECU if necessary, updating software, or resetting the communication network in the vehicle.

7. Should I attempt to clear the U1104 code on my 2018 Toyota RAV4 with a diagnostic tool?

Clearing the code without addressing the underlying issue may only temporarily resolve the symptom. It is recommended to diagnose and fix the root cause of the problem first.

8. Can a DIY enthusiast fix the U1104 code on a 2018 Toyota RAV4?

While some basic troubleshooting steps can be performed by DIY enthusiasts, addressing complex issues related to the driving support ECU may require professional expertise and specialized tools.

9. Will the U1104 code in a 2018 Toyota RAV4 affect the vehicle's overall performance?

The code may impact the functionality of driving support features, but it might not necessarily affect the general performance of the vehicle's engine or drivability.

10. How much does it cost to repair the U1104 code on a 2018 Toyota RAV4?

The cost of repairs can vary depending on the exact cause of the issue, the need for parts replacement, and labor costs. It's advisable to obtain estimates from qualified mechanics or service centers.