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U0078 Buick Code - Control Module Communication Low Speed CAN Bus Off

Quick Answer

The low-speed General Motor Local Area Network (GMLAN) serial data bus is used to communicate information between the devices. Common causes include Check for more codes, Faulty Control Module, Control Module harness is open or shorted. 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: U0078 Buick indicates Control Module Communication Low Speed CAN Bus Off.
Common causes: Common causes include Check for more codes, Faulty Control Module, Control Module harness is open or shorted.
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 3,582

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 Jul 20, 2023

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U0078 Buick Description

The low-speed General Motor Local Area Network (GMLAN) serial data bus is used to communicate information between the devices. The serial data is transmitted over a single wire to the appropriate devices. The low-speed GMLAN serial data circuits also connect directly to the Data Link Connector (DLC). The Diagnostic Trouble Code (DTC) sets when the device setting the DTC has attempted to establish communications on the serial data circuits more than 3 times in 5 s.

OBDII Code U0078 Buick - Control Module Communication Low Speed CAN Bus Off - AutoCodes.com — U0078 Buick Code - Control Module Communication Low Speed CAN Bus Off

What does this mean?

What are the Possible Causes of the DTC U0078 Buick?

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 U0078 Buick?

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 U0078 Buick 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 more information on how to fix the U0078 Buick 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 U0078 Buick Code

1. What does the OBDII code U0078 mean on a Buick?

The U0078 code indicates a communication issue on the Low-Speed CAN (Controller Area Network) bus, often referred to as "bus off," meaning the control modules cannot communicate properly.

2. What are the common symptoms of code U0078 in a Buick?

Symptoms can include the check engine light or other warning lights, failure of certain vehicle systems like infotainment or climate control, and erratic or unresponsive vehicle performance.

3. What causes the U0078 code to appear on a Buick?

Common causes include faulty wiring or connectors in the CAN bus system, a malfunctioning control module, or electrical interference from other components.

4. Can a weak battery cause the U0078 code on a Buick?

Yes, a weak or failing battery can cause voltage drops that disrupt communication on the CAN bus, potentially triggering the U0078 code.

5. How can I diagnose the U0078 code on my Buick?

Begin by inspecting the CAN bus wiring and connectors for damage or corrosion, check for loose connections, and test the battery and charging system for proper voltage.

6. Is it safe to drive with the U0078 code on a Buick?

Driving may still be possible, but itâ€™s not recommended since the code can indicate critical communication issues that affect vehicle safety and performance.

7. Can a faulty control module cause the U0078 code?

Yes, a control module with internal failure can disrupt communication on the Low-Speed CAN bus and trigger the U0078 code.

8. How much does it cost to repair the U0078 code on a Buick?

Repair costs can vary widely depending on the issue, ranging from $50 for minor wiring fixes to $1,000 or more if a control module needs replacement.

9. Can I fix the U0078 code on my Buick myself?

If the issue is related to a loose connector or corroded wiring, you may be able to fix it yourself. For complex electrical diagnostics or module replacement, professional help is recommended.

10. Will clearing the U0078 code with a scanner fix the issue on my Buick?

Clearing the code may turn off the warning temporarily, but it won't fix the underlying issue causing the communication problem. Proper diagnosis and repair are necessary.