AutoCodes – Generic – U0003

U0003 Code - High Speed CAN Communication Bus (+) Open

Quick Answer

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. 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: U0003 indicates High Speed CAN Communication Bus (+) Open.
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 19,353

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 U0003 Description

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Operating information and commands are exchanged among the devices. The devices have programmed information about what messages are needed to be exchanged on the serial data circuits. CAN bus uses two dedicated wires for communication. The wires are called CAN high and CAN low. When the CAN bus is in idle mode, both lines carry 2.5V. When data bits are being transmitted, the CAN high line goes to 3.75V, and the CAN low drops to 1.25V, thereby generating 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 supervised periodic message that includes the transmitter device availability has not been received.

OBDII Code U0003 - High Speed CAN Communication Bus (+) Open - AutoCodes.com — U0003 Code - High Speed CAN Communication Bus (+) Open

What does this mean?

What are the Possible Causes of the DTC U0003?

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 U0003?

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 U0003 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 U0003 code?

Need more information on how to fix the U0003 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0003 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 U0003 Code

1. What are the common symptoms of OBDII code U0003 (High Speed CAN Communication Bus (+) Open)?

- Common symptoms include issues with the vehicle's communication systems, such as loss of communication between control modules, warning lights on the dashboard, and erratic behavior of electronic components.

2. What are the possible causes of OBDII code U0003 (High Speed CAN Communication Bus (+) Open)?

- Possible causes may include damaged wiring or connectors in the high-speed CAN bus network, faulty control modules, water damage, or corrosion in the electrical connections.

3. How can I diagnose OBDII code U0003 (High Speed CAN Communication Bus (+) Open)?

- Diagnosing this code typically involves using a scan tool to check for other related trouble codes, inspecting the wiring and connectors in the CAN bus network, and performing continuity tests to identify the open circuit.

4. What should I do if I encounter OBDII code U0003 (High Speed CAN Communication Bus (+) Open)?

- If you encounter this code, it is recommended to first check all related fuses, wiring, and connectors for any visible damage. If no issues are found, further diagnostic testing by a professional technician may be required.

5. Can OBDII code U0003 (High Speed CAN Communication Bus (+) Open) be repaired without professional help?

- While simple issues like loose connectors or damaged wiring can sometimes be fixed by DIY enthusiasts, diagnosing and repairing the underlying cause of this code often requires professional equipment and expertise.

6. What are the potential risks of ignoring OBDII code U0003 (High Speed CAN Communication Bus (+) Open)?

- Ignoring this code can lead to continued communication issues between control modules, potentially causing safety hazards, malfunctions in critical systems, and overall poor vehicle performance.

7. How much does it typically cost to repair OBDII code U0003 (High Speed CAN Communication Bus (+) Open)?

- The cost of repairing this code can vary greatly depending on the root cause of the issue, the extent of the damage, and the labor rates of the repair shop. It is advisable to obtain multiple quotes for an accurate estimate.

8. Is it safe to drive with OBDII code U0003 (High Speed CAN Communication Bus (+) Open) present?

- It is not recommended to drive with this code present, as it can lead to unpredictable behavior of electronic systems in the vehicle. It is best to address the issue promptly to ensure safe operation.

9. Can extreme weather conditions cause OBDII code U0003 (High Speed CAN Communication Bus (+) Open)?

- Yes, extreme weather conditions such as exposure to moisture or temperature fluctuations can contribute to the development of an open circuit in the high-speed CAN bus network, triggering this fault code.

10. How long does it typically take to repair OBDII code U0003 (High Speed CAN Communication Bus (+) Open)?

- The repair time for this code can vary depending on the complexity of the issue and the availability of parts. In some cases, it may be a quick fix, while in others, it could take several hours or even days to fully resolve.