AutoCodes – GMC – U1026 GMC

U1026 GMC Code - Lost Communication with Transfer Case Control Module

Quick Answer

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Transfer Case Control Module, Transfer Case Control Module harness is open or shorted, Transfer Case 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: U1026 GMC indicates Lost Communication with Transfer Case Control Module.
Common causes: Common causes include Faulty Transfer Case Control Module, Transfer Case Control Module harness is open or shorted, Transfer Case 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.

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Code Popularity 5,814

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 21, 2023

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code U1026 GMC Description

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices. The devices have prerecorded information about what messages are needed 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 device as an availability indication of the transmitter device. Each message contains the identification number of the transmitter device. The Diagnostic Trouble Code (DTC) will be set when a supervised periodic message that includes the transmitter device availability has not been received.

OBDII Code U1026 GMC - Lost Communication with Transfer Case Control Module - AutoCodes.com — U1026 GMC Code - Lost Communication with Transfer Case Control Module

What does this mean?

What are the Possible Causes of the DTC U1026 GMC?

Faulty Transfer Case Control Module
Transfer Case Control Module harness is open or shorted
Transfer Case Control Module circuit poor electrical connection

How to Fix the DTC U1026 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 does this mean?

Code Tech Notes

This is typically an electrical wiring connection issue at one of the controllers being monitored by the manufacturer.
It can occur if:
Someone changes a battery while the ignition switch is left on, that is, left in the Run position.
Someone flashes/upgrades their engine controller - other modules unable to communicate with PCM during this process - this will set U1026 at a multitude of controllers on the vehicle - all false codes. Erase and carry on.
May need to disconnect both battery cables and touch them together for 15 seconds. Reattach battery cables, positive first, then negative and see if a soft reset helps.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U1026 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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Need Help with the Code?

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Information for Specific GMC Models

U1026 2014 GMC Sierra — Lost Communication with Transfer Case Control Module
U1026 2015 GMC Sierra — Lost Communication with Transfer Case Control Module
U1026 2016 GMC Sierra — Lost Communication with Transfer Case Control Module
U1026 2017 GMC Sierra — Lost Communication with Transfer Case Control Module
U1026 2018 GMC Sierra — Lost Communication with Transfer Case Control Module

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 U1026 GMC Code

1. What are the common symptoms of OBDII code U1026 GMC (Lost Communication with Transfer Case Control Module)?

- Common symptoms include the inability to shift into 4WD, illuminated warning lights on the dashboard, and issues with the transfer case functionality.

2. What are the possible causes of OBDII code U1026 GMC?

- The code U1026 GMC can be caused by a faulty transfer case control module, damaged wiring or connectors, a blown fuse, or a communication bus issue.

3. How can I diagnose the OBDII code U1026 GMC?

- Diagnosis typically involves using a scan tool to retrieve the code, checking the wiring and connectors for any damage, and testing the transfer case control module for proper functionality.

4. Can a weak battery cause the OBDII code U1026 GMC to appear?

- Yes, a weak or failing battery can sometimes cause communication issues between modules, leading to the U1026 code being triggered.

5. What are some repair tips for fixing OBDII code U1026 GMC?

- Repair tips may include checking and repairing any damaged wiring or connectors, replacing the transfer case control module if necessary, and ensuring all fuses related to the transfer case system are in good condition.

6. Is it safe to continue driving with the OBDII code U1026 GMC present?

- It is generally not recommended to continue driving with the U1026 code present, as it can affect the proper operation of the transfer case system, potentially leading to safety issues.

7. Can a software update fix the OBDII code U1026 GMC issue?

- In some cases, a software update provided by the manufacturer may address communication issues and resolve the U1026 code without the need for component replacement.

8. How much does it typically cost to repair OBDII code U1026 GMC?

- The cost of repairing the U1026 code can vary depending on the underlying cause, but it may range from $100 to $500 or more, including parts and labor.

9. Will resetting the code make it go away permanently?

- Resetting the code may temporarily clear the warning light, but if the underlying issue causing the U1026 code is not addressed, it is likely to reappear.

10. Can a DIY enthusiast fix the OBDII code U1026 GMC issue?

- Depending on the cause of the code, some DIY enthusiasts with the necessary tools and skills may be able to diagnose and repair the U1026 GMC code, but complex issues may require professional assistance.