AutoCodes – GMC – U1099 GMC

U1099 GMC Code - Loss Of Head-Up Display Communications

Quick Answer

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Common causes include Faulty Head-Up Display (HUD), Head-Up Display harness is open or shorted, Head-Up Display 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: U1099 GMC indicates Loss Of Head-Up Display Communications.
Common causes: Common causes include Faulty Head-Up Display (HUD), Head-Up Display harness is open or shorted, Head-Up Display 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 698

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 Apr 24, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code U1099 GMC Description

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for the state of health monitoring/node alive messages. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once an identification number is learned by a module, it will monitor for that module node alive message. Each module on the class 2 serial data circuit is required to send a Node Alive message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a Diagnostic Trouble Code (DTC) U1099 is set.

OBDII Code U1099 GMC - Loss Of Head-Up Display Communications - AutoCodes.com — U1099 GMC Code - Loss Of Head-Up Display Communications

What does this mean?

What are the Possible Causes of the DTC U1099 GMC?

Faulty Head-Up Display (HUD)
Head-Up Display harness is open or shorted
Head-Up Display circuit poor electrical connection

How to Fix the DTC U1099 GMC?

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 U1099 GMC 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 U1099 GMC code?

Need more information on how to fix the U1099 GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1099 GMC 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 U1099 GMC Code

1. What are the common symptoms of OBDII code U1099 GMC?

- Common symptoms include a loss of the head-up display (HUD) functionality, issues with the display screen, and potential communication errors.

2. What are the possible causes of OBDII code U1099 GMC?

- The code U1099 GMC typically indicates a loss of communication between the vehicle's control modules and the head-up display system. Possible causes may include wiring issues, a faulty control module, or a malfunctioning display unit.

3. How can I diagnose the OBDII code U1099 GMC?

- Diagnosing the code U1099 GMC may require using a diagnostic scanner to communicate with the vehicle's control modules and check for any communication errors related to the head-up display system.

4. What are some repair tips for fixing OBDII code U1099 GMC?

- Repair tips may include checking the wiring connections between the control modules and the head-up display unit, inspecting for any damaged wires or connectors, and testing the control modules for proper functionality.

5. Can I drive my vehicle with OBDII code U1099 GMC?

- While the vehicle may still be operational with the code U1099 GMC, it is recommended to address the issue promptly to ensure the proper functioning of the head-up display system and to prevent any potential safety hazards.

6. Is it safe to reset the OBDII code U1099 GMC without fixing the underlying issue?

- It is not recommended to simply reset the code without addressing the underlying communication issue, as this may lead to the problem recurring and potentially affecting other vehicle systems.

7. How much does it typically cost to repair OBDII code U1099 GMC?

- The cost of repairing the code U1099 GMC can vary depending on the specific cause of the issue, the extent of the repairs needed, and the labor rates at the repair facility. It is advisable to get a diagnosis from a professional technician to determine the exact cost.

8. Can a DIY enthusiast fix OBDII code U1099 GMC at home?

- While some basic troubleshooting steps can be performed at home, diagnosing and repairing the code U1099 GMC may require specialized tools and expertise. It is recommended to seek professional help for a comprehensive diagnosis and repair.

9. How long does it take to repair OBDII code U1099 GMC?

- The repair time for the code U1099 GMC can vary depending on the complexity of the issue and the availability of parts. Some repairs may be completed within a few hours, while others may take longer if extensive troubleshooting is required.

10. Are there any recalls or technical service bulletins related to OBDII code U1099 GMC?

- It is advisable to check with the manufacturer or a dealership for any recalls or technical service bulletins related to the code U1099 GMC, as they may provide additional information or guidance on addressing the issue.