AutoCodes – Mercury – U0004 Mercury

U0004 Mercury Code - High Speed CAN Communication Bus (+) Low

Quick Answer

Multiplexing is a method of sending 2 or more signals simultaneously over a single circuit. Common causes include Diagnosis of this Diagnostic Trouble Code (DTC) is accomplished via the vehicle symptom(s), Check for more codes, Faulty Control Module. 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: U0004 Mercury indicates High Speed CAN Communication Bus (+) Low.
Common causes: Common causes include Diagnosis of this Diagnostic Trouble Code (DTC) is accomplished via the vehicle symptom(s), Check for more codes, Faulty Control Module.
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 931

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 29, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0004 Mercury Description

Multiplexing is a method of sending 2 or more signals simultaneously over a single circuit. Multiplexing allows 2 or more electronic modules (nodes) to communicate over a twisted wire pair [data (+) and data (-)] network. The information or messages that can be communicated on these wires consists of commands, status or data. Multiplexing reduces the weight of the vehicle by reducing the number of redundant components and electrical wiring. The vehicle has 4 module communication networks connected to the DLC, located under the instrument panel. The communication networks are: HEV High Speed Controller Area Network (HS-CAN), High Speed Controller Area Network (HS-CAN), Medium Speed Controller Area Network (MS-CAN) and Infotainment Controller Area Network (I-CAN). The Diagnostic Trouble Code (DTC) U0004 sets when a High Speed Controller Area Network (HS-CAN) fault was present at a point in time. The fault is not currently present since the module is communicating with the scan tool.

OBDII Code U0004 Mercury - High Speed CAN Communication Bus (+) Low - AutoCodes.com — U0004 Mercury Code - High Speed CAN Communication Bus (+) Low

What does this mean?

What are the Possible Causes of the DTC U0004 Mercury?

Diagnosis of this Diagnostic Trouble Code (DTC) is accomplished via the vehicle symptom(s)
Check for more codes
Faulty Control Module
Control Module harness is open or shorted
Control Module circuit poor electrical connection

How to Fix the DTC U0004 Mercury?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U0004 Mercury 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 U0004 Mercury code?

Need more information on how to fix the U0004 Mercury code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0004 Mercury code diagnosed by a professional: Find a repair shop in your area

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 U0004 Mercury Code

1. What are the common symptoms of OBDII code U0004 on a Mercury vehicle?

- Common symptoms may include issues with the vehicle's transmission, engine performance, or dashboard warning lights illuminating.

2. What are the possible causes of the U0004 code on a Mercury vehicle?

- The U0004 code can be triggered by issues such as wiring faults, faulty connectors, a malfunctioning high-speed CAN communication bus, or a problem with the control modules.

3. How can I diagnose the U0004 code on my Mercury vehicle?

- Diagnosis typically involves using an OBDII scanner to retrieve the code, checking the high-speed CAN communication bus for faults, inspecting wiring and connectors, and testing the control modules.

4. Can I still drive my Mercury with the U0004 code present?

- It is not recommended to drive the vehicle with the U0004 code present, as it may lead to further damage or safety issues. Prompt diagnosis and repair are advised.

5. How can I repair the U0004 code on my Mercury?

- Repair options may include repairing or replacing damaged wiring, fixing faulty connectors, addressing issues with the control modules, and ensuring proper communication on the high-speed CAN bus.

6. Is the U0004 code a serious issue on a Mercury vehicle?

- The U0004 code should be addressed promptly to prevent potential performance issues, transmission problems, or further damage to the vehicle's systems.

7. Can a DIY enthusiast fix the U0004 code on a Mercury, or is professional help required?

- While some basic troubleshooting steps can be taken by DIY enthusiasts, addressing the U0004 code may require specialized tools and expertise, making professional help advisable.

8. What should I do if the U0004 code keeps coming back on my Mercury after repair?

- If the U0004 code keeps returning after repair, it may indicate an underlying issue that was not fully resolved. Revisiting the diagnosis and repair process is recommended.

9. Are there any preventive measures to avoid the U0004 code on a Mercury vehicle?

- Regular maintenance checks, ensuring proper electrical connections, and addressing any warning signs promptly can help prevent issues that may trigger the U0004 code.

10. How much does it typically cost to repair the U0004 code on a Mercury vehicle?

- Repair costs for the U0004 code can vary depending on the underlying issue, parts needed, and labor rates. It is advisable to consult with a mechanic for an accurate estimate.