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Engine-Codes – Generic – U1104

U1104 Code - Lost Communication with Driving Support ECU

Quick Answer

The U1104 diagnostic trouble code indicates that the vehicle's onboard computer system has lost communication with the Driving Support Electronic Control Unit (ECU). Common causes include Faulty wiring or connections between the onboard computer system and the Driving Support ECU, Malfunctioning Driving Support ECU, Software or firmware issues within the onboard 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 indicates Lost Communication with Driving Support ECU.
Common causes
Common causes include Faulty wiring or connections between the onboard computer system and the Driving Support ECU, Malfunctioning Driving Support ECU, Software or firmware issues within the onboard 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 Aug 18, 2024
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Code U1104 Description

The U1104 diagnostic trouble code indicates that the vehicle's onboard computer system has lost communication with 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 significantly impact the vehicle's performance and safety features.

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

Common Causes of U1104

  1. Faulty wiring or connections between the onboard computer system and the Driving Support ECU
  2. Malfunctioning Driving Support ECU
  3. Software or firmware issues within the onboard computer system
  4. Electrical interference or communication bus faults

Symptoms of U1104

  1. Warning lights illuminated on the dashboard
  2. Loss of driving support features (e.g., adaptive cruise control, lane departure warning)
  3. Erratic behavior of driving support systems
  4. Vehicle may not start or may go into limp mode

How to Fix U1104

  1. Begin by checking the wiring and connections between the onboard computer system and the Driving Support ECU for any signs of damage or corrosion.
  2. Use a diagnostic scanner to reset the communication between the two ECUs and see if the code reappears.
  3. If the issue persists, test the Driving Support ECU for proper functionality and replace if necessary.
  4. Check for any software or firmware updates for the onboard computer system and perform updates as needed.
  5. If all else fails, consult with a professional technician to further diagnose and repair the issue.

Cost to Fix U1104

The typical repair costs for addressing the U1104 code can vary depending on the specific cause of the communication loss. Parts such as a new Driving Support ECU or wiring harnesses can range from $200 to $1000, while labor costs can range from $100 to $300. Additional diagnostic time may also be required, which can add to the overall cost. It's recommended to consult with a local auto repair shop to get an accurate estimate based on your vehicle's make and model.

What does this mean?

Tech Notes for U1104

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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Code U1104 Information for Specific Makes

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 Code

1. What does the OBDII code U1104 mean?

U1104 indicates a loss of communication with the Driving Support ECU, which manages certain driver assistance features like adaptive cruise control or lane-keeping systems.

2. What are the common symptoms of code U1104?

Symptoms may include malfunctioning driver assistance features, warning lights on the dashboard, and intermittent loss of functionality in systems like adaptive cruise control.

3. What causes code U1104 to appear?

Common causes include faulty wiring or connectors, a malfunctioning Driving Support ECU, issues with the CAN bus network, or low system voltage.

4. Can a weak battery cause the U1104 code?

Yes, a weak or failing battery can cause communication errors like U1104 due to low voltage disrupting the ECU's operation.

5. How do I diagnose the U1104 code?

Start by checking the wiring and connectors associated with the Driving Support ECU, then scan the vehicle’s CAN bus network for other communication issues. Verify the battery and charging system as well.

6. Is it safe to drive with the U1104 code?

While the vehicle may still be drivable, driver assistance features may not function properly, which could compromise safety depending on driving conditions.

7. How can I fix the U1104 code?

Repairs may include inspecting and repairing damaged wiring, cleaning or replacing corroded connectors, reprogramming the ECU, or replacing the Driving Support ECU if necessary.

8. Do I need to replace the Driving Support ECU if I get the U1104 code?

Not necessarily. The issue could be related to wiring, connectors, or a software glitch. Proper diagnostics should be performed before replacing the ECU.

9. Can a software update resolve the U1104 code?

In some cases, a software update for the ECU can fix communication errors if the issue is related to outdated programming.

10. How much does it cost to fix the U1104 code?

The cost varies depending on the issue. Simple wiring repairs may cost $100-$200, while ECU replacement could range from $500 to $1,500, including parts and labor.

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