AutoCodes – Generic – U0073

U0073 Code - Control Module Communication Bus 'A' Off

Quick Answer

Modules connected to the high-speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Module/Device that is not communicating, Module/Device harness is open or shorted, Module/Device 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: U0073 indicates Control Module Communication Bus 'A' Off.
Common causes: Common causes include Faulty Module/Device that is not communicating, Module/Device harness is open or shorted, Module/Device 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 57,983

How popular is this code, among other codes? Medium

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 19, 2023

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes ▶
Cost to Diagnose
FAQs
Comments
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Code U0073 Description

Modules connected to the 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 modules. The modules have prerecorded information about what messages need to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. The supervision time-out period is 250 ms. Each message contains the identification number of the transmitter module. The Diagnostic Trouble Code (DTC) will be set 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 U0073 - Control Module Communication Bus 'A' Off - AutoCodes.com — U0073 Code - Control Module Communication Bus 'A' Off

What does this mean?

What are the Possible Causes of the DTC U0073?

Faulty Module/Device that is not communicating
Module/Device harness is open or shorted
Module/Device circuit poor electrical connection

How to Fix the DTC U0073?

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 does this mean?

Code Tech Notes

When there are problems with the way different systems in a vehicle communicate with each other using a technology called Controller Area Network (CAN) communication, Diagnostic Trouble Codes (DTC) are displayed. These codes can be caused by issues with the main bus or branch of the communication network, or with the Electronic Control Units (ECUs) and sensors that make up the different systems. If you see code for both the CAN communication problems and internal or power source problems at the same time, you should focus on fixing the internal or power source problems first.

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U0073 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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Information for Specific Makes

U0073 Acura — Control Module Communication Bus OFF
U0073 Buick — Control Module Communication Bus OFF
U0073 Cadillac — Control Module Communication Bus OFF
U0073 Chevrolet — Control Module Communication Bus OFF
U0073 Ford — Control Module Communication Bus OFF
U0073 GMC — Control Module Communication Bus OFF
U0073 Honda — Control Module Communication Bus OFF
U0073 Hummer — Control Module Communication Bus OFF
U0073 Lexus — Control Module Communication Bus Off
U0073 Lincoln — Control Module Communication Bus OFF
U0073 Mercury — Control Module Communication Bus OFF
U0073 Pontiac — Control Module Communication Bus OFF
U0073 Saturn — Control Module Communication Bus OFF
U0073 Scion — Control Module Communication Bus Off
U0073 Toyota — Control Module Communication Bus Off

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 U0073 Code

1. What does the OBDII code U0073 mean?

The U0073 code indicates that there is a communication issue on the Control Module Communication Bus 'A,' which is part of the vehicle's Controller Area Network (CAN).

2. What are the common symptoms of code U0073?

Symptoms may include a check engine light, erratic or non-functioning electronic systems, failure of certain modules to communicate, or the vehicle entering limp mode.

3. What causes the U0073 code to appear?

Common causes include a faulty control module, damaged CAN wiring, poor electrical connections, low battery voltage, or issues with the CAN bus network.

4. How is the U0073 code diagnosed?

Technicians use a scan tool to check for additional codes, inspect the CAN bus wiring and connectors for damage, and test the voltage and resistance in the communication circuit.

5. Can a weak battery cause the U0073 code?

Yes, a weak or failing battery can result in low voltage, which may disrupt module communication and trigger the U0073 code.

6. Can I still drive my car with the U0073 code?

Driving with the U0073 code is not recommended, as it may cause critical systems to malfunction or the vehicle to enter limp mode.

7. How is code U0073 fixed?

Repairs may include replacing or repairing damaged wiring, ensuring proper connections, reprogramming or replacing a faulty control module, or addressing battery and voltage issues.

8. Can a loose connector cause the U0073 code?

Yes, a loose or corroded connector in the CAN bus circuit can disrupt communication and trigger the U0073 code.

9. Is the U0073 code specific to one control module?

No, the U0073 code refers to a general communication issue on the CAN bus and may involve multiple control modules.

10. How much does it cost to fix the U0073 code?

The repair cost depends on the issue. Simple fixes like repairing wiring or connectors may cost $100â€“$300, while replacing a control module can exceed $1,000.