AutoCodes – Generic – U0042

U0042 Code - Vehicle Communication Bus 'B' (-) 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: U0042 indicates Vehicle Communication Bus 'B' (-) 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 5,149

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 U0042 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 U0042 - Vehicle Communication Bus 'B' (-) Open - AutoCodes.com — U0042 Code - Vehicle Communication Bus 'B' (-) Open

What does this mean?

What are the Possible Causes of the DTC U0042?

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 U0042?

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 U0042 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 U0042 code?

Need more information on how to fix the U0042 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0042 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 U0042 Code

1. What are the common symptoms of OBDII code U0042?

The common symptoms of OBDII code U0042, Vehicle Communication Bus 'B' (-) Open, may include issues with the vehicle's communication systems, such as problems with the transmission, engine, or other control modules.

2. What are some possible causes of OBDII code U0042?

Possible causes of OBDII code U0042 include damaged wiring or connectors in the vehicle communication network, a faulty control module, or a problem with the communication bus itself.

3. How is OBDII code U0042 diagnosed?

Diagnosing OBDII code U0042 typically involves using a diagnostic scanner to retrieve the fault code, performing a visual inspection of the wiring and connectors in the communication network, and conducting further testing to pinpoint the exact cause of the issue.

4. Can OBDII code U0042 be repaired at home?

While some simple wiring or connector issues related to OBDII code U0042 may be resolved at home, it is recommended to consult with a professional mechanic for a thorough diagnosis and repair to ensure the problem is properly addressed.

5. How serious is OBDII code U0042?

OBDII code U0042 should be addressed promptly to prevent potential communication failures between various vehicle control modules, which could lead to performance issues or safety concerns while driving.

6. Is it safe to drive with OBDII code U0042?

It is not recommended to drive with OBDII code U0042 present, as the underlying communication bus issue could affect the proper functioning of critical vehicle systems.

7. Can resetting the OBDII code U0042 resolve the issue?

Simply resetting the code may temporarily clear the warning light, but it will not fix the root cause of the communication bus 'B' (-) open problem. It is important to diagnose and repair the issue to prevent it from recurring.

8. How much does it cost to repair OBDII code U0042?

The cost of repairing OBDII code U0042 can vary depending on the exact cause of the issue, the extent of the repairs needed, and the labor rates of the mechanic or repair shop.

9. Is OBDII code U0042 specific to a certain make or model of vehicle?

OBDII code U0042 can occur in various makes and models of vehicles that are equipped with an OBDII system, as it relates to a communication bus issue that is fundamental to modern vehicle electronics.

10. Are there any preventive measures to avoid OBDII code U0042?

Regular maintenance and inspections of the vehicle's wiring harnesses, connectors, and control modules can help prevent issues like OBDII code U0042 from occurring.