AutoCodes – Generic – U0044

U0044 Code - Vehicle Communication Bus 'B' (-) High

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: U0044 indicates Vehicle Communication Bus 'B' (-) High.
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 4,331

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 U0044 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 U0044 - Vehicle Communication Bus 'B' (-) High - AutoCodes.com — U0044 Code - Vehicle Communication Bus 'B' (-) High

What does this mean?

What are the Possible Causes of the DTC U0044?

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 U0044?

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 U0044 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 U0044 code?

Need more information on how to fix the U0044 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0044 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 U0044 Code

1. What are the common symptoms of OBDII code U0044 (Vehicle Communication Bus 'B' (-) High)?

The common symptoms of code U0044 include issues with communication between control modules, erratic behavior of electronic systems, and in some cases, the vehicle may not start.

2. What are the possible causes of OBDII code U0044?

Possible causes of code U0044 include faulty wiring or connections in the communication bus 'B', a malfunctioning control module, water damage, or a short circuit in the communication network.

3. How can I diagnose OBDII code U0044?

Diagnosing code U0044 typically involves using a professional OBDII scanner to read the code and identify the specific module or circuit that is causing the communication bus 'B' (-) high issue. Thoroughly inspecting the wiring and connections for any visible damage can also help in diagnosis.

4. Can OBDII code U0044 be fixed at home?

Depending on the underlying cause, fixing code U0044 may or may not be a DIY task. If it is a simple wiring issue or loose connection, you may be able to fix it at home. However, more complex issues like a faulty control module may require professional diagnosis and repair.

5. What are some repair tips for fixing OBDII code U0044?

Repair tips for code U0044 include checking and repairing any damaged wiring or connections in the communication bus 'B', ensuring proper grounding of the control modules, and performing a thorough inspection of the entire communication network.

6. Can driving with OBDII code U0044 cause further damage to the vehicle?

Continuing to drive with code U0044 present can potentially cause further damage to the vehicle's electronic systems, as the communication issues may affect the proper functioning of various control modules. It is advisable to address the issue promptly.

7. How much does it cost to repair OBDII code U0044?

The cost of repairing code U0044 can vary depending on the underlying cause, the extent of the damage, and whether you choose to do the repairs yourself or take your vehicle to a professional mechanic. Costs may range from a simple wiring repair to replacing a faulty control module.

8. Is it safe to clear the OBDII code U0044 without fixing the underlying issue?

Clearing the OBDII code U0044 without addressing the underlying issue is not recommended, as the problem may persist and potentially lead to further complications with the vehicle's electronic systems. It is best to diagnose and fix the root cause of the code.

9. How long does it take to repair OBDII code U0044?

The time required to repair code U0044 can vary depending on the complexity of the issue and the availability of parts. Simple fixes like repairing wiring may take a short amount of time, while more complex repairs involving control module replacement could take longer.

10. Can a faulty battery cause OBDII code U0044 to appear?

Yes, a faulty or weak battery can potentially cause OBDII code U0044 to appear, as it may lead to voltage fluctuations in the vehicle's electrical system, affecting the communication bus 'B'. It's important to ensure the battery is in good condition when troubleshooting this code.