AutoCodes – Generic – U1104

U1104 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 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 21,660

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
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

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

What does this mean?

What are the Possible Causes of the DTC U1104?

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?

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 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.

Need more information about the U1104 code?

Need more information on how to fix the U1104 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1104 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U1104 Chrysler — Invalid Or Missing Data For Dynamics Sensor
U1104 Dodge — Invalid Or Missing Data For Dynamics Sensor
U1104 Jeep — Invalid Or Missing Data For Dynamics Sensor
U1104 Lexus — Lost Communication with Driving Support ECU
U1104 RAM — Invalid Or Missing Data For Dynamics Sensor
U1104 Toyota — 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 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 vehicleâ€™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.