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U0078 Cadillac 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 Cadillac 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 3,063

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

What does this mean?

What are the Possible Causes of the DTC U0078 Cadillac?

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 Cadillac?

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 Cadillac 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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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 Cadillac Code

1. What are common symptoms of OBDII code U0078 on a Cadillac?

The common symptoms of U0078 include issues with the vehicle's communication network, such as intermittent or complete loss of communication between control modules.

2. What causes the U0078 code to appear in a Cadillac?

The U0078 code is typically triggered when there is a malfunction in the low-speed Controller Area Network (CAN) bus communication system, often due to a faulty control module or wiring issues.

3. How can I diagnose the U0078 code on my Cadillac?

To diagnose the U0078 code, it is recommended to use an OBDII scanner to retrieve the specific fault codes and then perform a thorough inspection of the low-speed CAN bus network, including checking for loose connections and damaged wiring.

4. Can a DIYer repair the U0078 code issue on a Cadillac?

While some basic troubleshooting steps can be performed by DIYers, addressing the U0078 code often requires advanced diagnostic equipment and knowledge. It is recommended to consult a professional mechanic for proper diagnosis and repair.

5. Is it safe to drive with the U0078 code illuminated in a Cadillac?

It is not recommended to drive with the U0078 code present, as it may lead to potential communication failure between critical control modules in the vehicle, impacting overall performance and safety.

6. How much does it cost to repair the U0078 code on a Cadillac?

The cost of repairing the U0078 code can vary depending on the underlying cause of the issue. It is advisable to obtain quotes from reputable mechanics or dealerships for an accurate estimate.

7. What are some common repair tips for fixing the U0078 code on a Cadillac?

Common repair tips for addressing the U0078 code include checking and repairing any damaged wiring, ensuring proper connections between control modules, and updating software or firmware as needed.

8. Can a bad battery cause the U0078 code to appear in a Cadillac?

A weak or faulty battery can potentially lead to communication issues in the vehicle, including triggering the U0078 code. It is advisable to check the battery's condition as part of the diagnostic process.

9. Will disconnecting the battery reset the U0078 code in a Cadillac?

Disconnecting the battery may temporarily clear the code, but it is not a recommended method for resolving the underlying issue causing the U0078 code. It is best to address the root cause of the problem for a lasting solution.

10. How can I prevent the U0078 code from reoccurring in my Cadillac?

To prevent the U0078 code from reoccurring, it is essential to maintain the vehicle's electrical system, perform regular inspections, and address any communication or wiring issues promptly to ensure proper functioning of the low-speed CAN bus network.