AutoCodes – Generic – U0299

U0299 Code - Lost Communication With DC To DC Converter Control Module 'B'

Quick Answer

A Controller Area Network (CAN) is a vehicle bus standard designed to interconnect automotive devices without a host computer. Common causes include Faulty DC To DC Converter Control Module 'B', DC To DC Converter Control Module 'B' harness is open or shorted, DC To DC Converter Control Module 'B' circuit poor electrical connection. 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: U0299 indicates Lost Communication With DC To DC Converter Control Module 'B'.
Common causes: Common causes include Faulty DC To DC Converter Control Module 'B', DC To DC Converter Control Module 'B' harness is open or shorted, DC To DC Converter Control Module 'B' circuit poor electrical connection.
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 3,918

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 Apr 06, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0299 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 periodic message from the DC To DC Converter Control Module 'B' has not been received.

OBDII Code U0299 - Lost Communication With DC To DC Converter Control Module 'B' - AutoCodes.com — U0299 Code - Lost Communication With DC To DC Converter Control Module 'B'

What does this mean?

What are the Possible Causes of the DTC U0299?

Faulty DC To DC Converter Control Module 'B'
DC To DC Converter Control Module 'B' harness is open or shorted
DC To DC Converter Control Module 'B' circuit poor electrical connection

How to Fix the DTC U0299?

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 U0299 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 U0299 code?

Need more information on how to fix the U0299 code? Get Access to Factory Service Manuals

Need Help with the Code?

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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 U0299 Code

What does the OBDII code U0299 mean?

U0299 indicates a loss of communication with the DC-to-DC converter control module 'B', which typically manages high-voltage power conversion in hybrid or electric vehicles.

What are the common symptoms of code U0299?

Symptoms may include warning lights on the dashboard, reduced vehicle performance, charging system issues, or failure to start the vehicle.

What causes the U0299 code to appear?

Common causes include faulty wiring or connectors, a malfunctioning DC-to-DC converter control module, software glitches, or issues with the vehicleâ€™s communication network.

Can I drive my car with a U0299 code active?

Driving with this code active may cause performance problems or damage to the electrical system. Itâ€™s recommended to address the issue promptly.

How do I diagnose the U0299 code?

Start by inspecting the wiring and connectors related to the DC-to-DC converter module. Use a diagnostic scan tool to verify communication errors and check for other related codes.

What tools are needed to troubleshoot U0299?

Youâ€™ll need an OBDII scan tool capable of reading manufacturer-specific codes, a multimeter to check electrical connections, and possibly wiring diagrams for your vehicle.

How do I fix the U0299 code?

Repairs may include replacing damaged wiring, reconnecting loose connectors, updating module software, or replacing a faulty DC-to-DC converter control module.

Can a software update resolve code U0299?

Yes, in some cases, updating the vehicleâ€™s software or firmware can resolve communication errors with the DC-to-DC converter module.

How much does it cost to repair the U0299 code?

Costs vary depending on the root cause, but repairs could range from $100 for wiring fixes to over $1,000 if the DC-to-DC converter control module needs replacement.

What happens if I ignore the U0299 code?

Ignoring the code may lead to further electrical system issues, reduced fuel efficiency in hybrids, or complete vehicle shutdown in severe cases.