AutoCodes – Generic – U0077

U0077 Code - Control Module Communication Chassis Expansion CAN Bus

Quick Answer

The devices connected to the chassis high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. 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: U0077 indicates Control Module Communication Chassis Expansion CAN Bus.
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 25,514

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 U0077 Description

The devices connected to the chassis high speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices when the ignition switch is in any position other than OFF. The chassis high speed GMLAN serial data bus uses terminating resistors that are in parallel with the chassis high speed GMLAN (+) and (-) circuits. The Diagnostic Trouble Code (DTC) sets when a supervised periodic message that includes the transmitter device availability has not been received.

OBDII Code U0077 - Control Module Communication Chassis Expansion CAN Bus - AutoCodes.com — U0077 Code - Control Module Communication Chassis Expansion CAN Bus

What does this mean?

What are the Possible Causes of the DTC U0077?

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 U0077?

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 U0077 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 U0077 code?

Need more information on how to fix the U0077 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U0077 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U0077 Buick — Control Module Communication Chassis Expansion CAN Bus
U0077 Cadillac — Control Module Communication Chassis Expansion CAN Bus
U0077 Chevrolet — Control Module Communication Chassis Expansion CAN Bus
U0077 GMC — Control Module Communication Chassis Expansion CAN Bus

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 U0077 Code

1. What are the common symptoms of OBDII code U0077?

The common symptoms of OBDII code U0077 include issues with communication between various control modules in the vehicle, such as warning lights on the dashboard, erratic behavior of electronic components, and possible difficulty starting the vehicle.

2. What causes OBDII code U0077 to trigger?

OBDII code U0077 is typically triggered by a failure or disruption in communication on the Chassis Expansion CAN Bus, which connects various control modules related to the vehicle's chassis systems.

3. How can I diagnose the cause of OBDII code U0077?

Diagnosing the cause of OBDII code U0077 usually involves using a diagnostic scanner to retrieve the specific fault codes stored in the affected control modules. Additionally, checking the wiring and connections related to the Chassis Expansion CAN Bus is essential.

4. What are some repair tips for fixing OBDII code U0077?

Repairing OBDII code U0077 often involves inspecting and repairing any damaged wiring or connections on the Chassis Expansion CAN Bus. Resetting the fault codes and retesting the system after repairs can help ensure the issue is resolved.

5. Can OBDII code U0077 be fixed without professional help?

While some basic troubleshooting steps can be taken by DIY enthusiasts, fixing OBDII code U0077 may require advanced diagnostic tools and expertise. It is recommended to seek assistance from a professional mechanic for accurate diagnosis and repair.

6. Is it safe to continue driving with OBDII code U0077 present?

Continuing to drive with OBDII code U0077 present is not recommended, as it can lead to further issues with the vehicle's electronic systems. It is best to address the underlying cause of the code as soon as possible to prevent potential safety hazards.

7. How much does it cost to repair OBDII code U0077?

The cost of repairing OBDII code U0077 can vary depending on the specific cause of the issue, the extent of the damage, and labor rates in your area. It is advisable to obtain quotes from local mechanics or repair shops for an accurate estimate.

8. Can a low battery voltage cause OBDII code U0077 to trigger?

Yes, a low battery voltage or electrical system issues can sometimes lead to the triggering of OBDII code U0077. Ensuring the battery and charging system are in good condition is essential for proper communication between control modules.

9. Will resetting the fault codes make OBDII code U0077 disappear permanently?

Simply resetting the fault codes associated with OBDII code U0077 may temporarily make the warning lights disappear, but if the underlying issue is not addressed, the code is likely to reappear once the system detects the communication problem again.

10. Are there specific vehicle makes and models more prone to OBDII code U0077?

While OBDII code U0077 can potentially occur in any vehicle with a Chassis Expansion CAN Bus, certain makes and models known for electronic system complexities may be more prone to experiencing communication issues leading to this code.