AutoCodes – GMC – U1147 GMC

U1147 GMC Code - Lost Communication With Onstar

Quick Answer

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Common causes include Faulty Onstar, Onstar harness is open or shorted, Onstar 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: U1147 GMC indicates Lost Communication With Onstar.
Common causes: Common causes include Faulty Onstar, Onstar harness is open or shorted, Onstar 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 546

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
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Code U1147 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) U1147 is set.

OBDII Code U1147 GMC - Lost Communication With Onstar - AutoCodes.com — U1147 GMC Code - Lost Communication With Onstar

What does this mean?

What are the Possible Causes of the DTC U1147 GMC?

Faulty Onstar
Onstar harness is open or shorted
Onstar circuit poor electrical connection

How to Fix the DTC U1147 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 U1147 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.

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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 U1147 GMC Code

1. What are the common symptoms of OBDII code U1147 GMC (Lost Communication With Onstar)?

- Common symptoms include the Onstar system not functioning properly, a loss of communication with Onstar services, and potential issues with vehicle diagnostics.

2. What are the possible causes of OBDII code U1147 GMC?

- The code U1147 GMC is typically triggered by a malfunction in the Onstar module, faulty wiring or connections related to the Onstar system, or an issue with the vehicle's communication network.

3. How can I diagnose the cause of OBDII code U1147 GMC?

- Diagnosis involves checking the Onstar module for proper functioning, inspecting wiring and connections for any damage or loose connections, and using a diagnostic scanner to assess the communication network.

4. Can I still drive my vehicle with OBDII code U1147 GMC?

- While the vehicle may still be drivable with this code, it is recommended to address the issue promptly to ensure the Onstar system functions correctly and to prevent any potential underlying communication network problems.

5. How can I repair OBDII code U1147 GMC?

- Repair options include checking and repairing any damaged wiring or connections, replacing the Onstar module if necessary, and resetting the code using a diagnostic scanner after the repairs have been made.

6. Are there any DIY tips for troubleshooting OBDII code U1147 GMC?

- DIY tips include visually inspecting wiring and connections for any obvious issues, checking fuses related to the Onstar system, and ensuring the vehicle's battery is in good condition.

7. Will resetting the OBDII code U1147 GMC resolve the issue?

- Resetting the code is a temporary solution and may not address the underlying problem causing the communication loss with Onstar. It is important to diagnose and repair the root cause of the issue.

8. Can a dealership or mechanic help with fixing OBDII code U1147 GMC?

- Yes, a dealership or qualified mechanic with experience in diagnosing and repairing Onstar system issues can assist in resolving OBDII code U1147 GMC.

9. Is OBDII code U1147 GMC a serious issue?

- While the code itself may not directly affect the drivability of the vehicle, it is important to address it promptly to ensure the proper functioning of the Onstar system and to prevent potential communication network problems.

10. How can I prevent OBDII code U1147 GMC from occurring in the future?

- Regularly checking the Onstar system for any signs of malfunction, keeping wiring and connections well-maintained, and addressing any related issues promptly can help prevent the recurrence of code U1147 GMC.