AutoCodes – Generic – U0043

U0043 Code - Vehicle Communication Bus 'B' (-) Low

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: U0043 indicates Vehicle Communication Bus 'B' (-) 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 5,630

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 U0043 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 U0043 - Vehicle Communication Bus 'B' (-) Low - AutoCodes.com — U0043 Code - Vehicle Communication Bus 'B' (-) Low

What does this mean?

What are the Possible Causes of the DTC U0043?

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 U0043?

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 U0043 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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Need Help with the Code?

Get the U0043 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 U0043 Code

1. What are the common symptoms of OBDII code U0043 (Vehicle Communication Bus 'B' (-) Low)?

- Common symptoms include issues with the vehicle's communication system, such as difficulty connecting to diagnostic tools, malfunctioning infotainment systems, and warning lights on the dashboard.

2. What are the possible causes of OBDII code U0043?

- Possible causes of this code include damaged wiring or connectors in the communication network, a faulty communication module, or a problem with the power supply to the communication bus.

3. How can I diagnose OBDII code U0043?

- Diagnosing this code typically involves using a scan tool to check for other related codes, inspecting the wiring and connectors in the communication network, and testing the communication modules for proper function.

4. Can driving with OBDII code U0043 cause further damage to the vehicle?

- Continuing to drive with this code may lead to issues with other vehicle systems that rely on the communication bus, potentially resulting in further damage or malfunctions.

5. How can I repair OBDII code U0043?

- Repairing this code often involves repairing or replacing damaged wiring or connectors, checking and replacing communication modules as needed, and ensuring proper power supply to the communication bus.

6. Is it safe to continue driving my vehicle with OBDII code U0043 present?

- It is not recommended to continue driving with this code present, as it may lead to further communication system malfunctions and potential safety hazards.

7. How much does it typically cost to fix OBDII code U0043?

- The cost of fixing this code can vary depending on the specific cause of the issue, but it may involve labor costs for diagnosis and repair, as well as the cost of any replacement parts needed.

8. Can OBDII code U0043 be triggered by a loose or corroded battery connection?

- Yes, a loose or corroded battery connection can disrupt the power supply to the communication bus and trigger code U0043.

9. Are there any DIY repair tips for OBDII code U0043?

- DIY repair tips for this code may include checking and tightening any loose connections, inspecting wiring for damage, and ensuring the battery terminals are clean and secure.

10. Will resetting the OBDII codes clear U0043 permanently?

- Resetting the OBDII codes may temporarily clear U0043, but if the underlying issue causing the code is not addressed, it is likely to reappear.