AutoCodes – GMC – U1023 GMC

U1023 GMC Code - Lost Communications With Hybrid Control Module

Quick Answer

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Common causes include Faulty Hybrid Control Module (HCM), Hybrid Control Module harness is open or shorted, Hybrid Control Module 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: U1023 GMC indicates Lost Communications With Hybrid Control Module.
Common causes: Common causes include Faulty Hybrid Control Module (HCM), Hybrid Control Module harness is open or shorted, Hybrid Control Module 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 479

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 22, 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 U1023 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) U1023 is set.

OBDII Code U1023 GMC - Lost Communications With Hybrid Control Module - AutoCodes.com — U1023 GMC Code - Lost Communications With Hybrid Control Module

What does this mean?

What are the Possible Causes of the DTC U1023 GMC?

Faulty Hybrid Control Module (HCM)
Hybrid Control Module harness is open or shorted
Hybrid Control Module circuit poor electrical connection

How to Fix the DTC U1023 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 U1023 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 U1023 GMC code?

Need more information on how to fix the U1023 GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1023 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 U1023 GMC Code

1. What are common symptoms of OBDII code U1023 in a GMC related to lost communications with the hybrid control module?

- Common symptoms include poor fuel efficiency, loss of power, and issues with starting or running the vehicle.

2. What are the possible causes of OBDII code U1023 in a GMC indicating lost communications with the hybrid control module?

- Possible causes include a faulty hybrid control module, damaged wiring or connectors, or issues with the communication network.

3. How can I diagnose the OBDII code U1023 in a GMC if I suspect a problem with the hybrid control module communication?

- Diagnose the code by checking the wiring and connectors for damage, testing the hybrid control module for functionality, and verifying communication signals.

4. Can a DIY enthusiast repair OBDII code U1023 in a GMC related to lost communications with the hybrid control module?

- Repairing this code may require specialized tools and knowledge, so it is recommended to consult a professional mechanic for proper diagnosis and repair.

5. Are there any specific repair tips for addressing OBDII code U1023 in a GMC associated with the hybrid control module communication issue?

- Ensure all wiring and connectors related to the hybrid control module are in good condition, and consider consulting a GMC dealership for specific repair guidance.

6. Is it safe to continue driving my GMC with the OBDII code U1023 indicating lost communications with the hybrid control module?

- It's not recommended to drive your vehicle with unresolved communication issues, as it may lead to further damage or safety concerns. Seek professional help promptly.

7. How much does it typically cost to repair OBDII code U1023 in a GMC related to the hybrid control module communication problem?

- Repair costs can vary depending on the exact cause of the issue, but expect to pay for diagnostic time, parts replacement, and labor fees from a mechanic.

8. Can a software update fix the OBDII code U1023 in a GMC indicating lost communications with the hybrid control module?

- In some cases, a software update provided by GMC may address communication issues with the hybrid control module. Check with a dealership for available updates.

9. Will resetting the OBDII code U1023 in a GMC resolve the lost communications problem with the hybrid control module?

- Simply clearing the code without addressing the underlying issue will not solve the communication problem. Proper diagnosis and repair are necessary for a lasting fix.

10. How can I prevent OBDII code U1023 from reoccurring in my GMC after repairing the communication issue with the hybrid control module?

- Regular maintenance, including checking wiring and connectors, and addressing any communication network issues promptly can help prevent the code from reoccurring.