AutoCodes – GMC – U1026 2018 GMC Sierra

U1026 2018 GMC Sierra 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 2018 GMC Sierra 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 221

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 2018 GMC Sierra 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 2018 GMC Sierra - Lost Communication with Transfer Case Control Module - AutoCodes.com — U1026 2018 GMC Sierra Code - Lost Communication with Transfer Case Control Module

What does this mean?

What are the Possible Causes of the DTC U1026 2018 GMC Sierra?

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 2018 GMC Sierra?

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 2018 GMC Sierra 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 U1026 2018 GMC Sierra code?

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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 U1026 2018 GMC Sierra Code

1. What does the OBDII code U1026 mean on a 2018 GMC Sierra?

The code U1026 indicates a lost communication with the Transfer Case Control Module (TCCM), meaning the module isnâ€™t receiving or sending proper signals to other components.

2. What are the common symptoms of the U1026 code in a 2018 GMC Sierra?

Symptoms include the 4WD system not functioning, the service 4WD message displaying on the dashboard, and potential loss of traction in certain driving conditions.

3. What causes the U1026 code on a 2018 GMC Sierra?

Common causes include a faulty TCCM, damaged or corroded wiring/connectors in the communication circuit, software issues, or low battery voltage affecting module operation.

4. How can I diagnose the U1026 code on my 2018 GMC Sierra?

Start by checking the wiring and connectors to the TCCM for damage or corrosion, ensuring the battery voltage is adequate, and scanning for other related codes to pinpoint the root issue.

5. Can I drive my 2018 GMC Sierra with the U1026 code active?

While the vehicle may be drivable, the 4WD system may not work properly, which could lead to traction issues in off-road or slippery conditions. Itâ€™s best to address the issue promptly.

6. How do I reset the U1026 code on my 2018 GMC Sierra?

After fixing the underlying issue, you can reset the code using an OBDII scanner. If the issue persists, the code will reappear.

7. What is the cost of repairing the U1026 code on a 2018 GMC Sierra?

Repair costs vary but can range from $100 for simple wiring repairs to $500 or more if the TCCM requires replacement.

8. Could a dead battery cause the U1026 code on a 2018 GMC Sierra?

Yes, a weak or dead battery can cause communication issues, including the U1026 code, as the modules may not function properly without adequate voltage.

9. How do I know if the TCCM is faulty on my 2018 GMC Sierra?

Signs of a faulty TCCM include the U1026 code, inability to switch between 2WD and 4WD modes, and no communication with the module during diagnostics.

10. Can a software update fix the U1026 code on a 2018 GMC Sierra?

In some cases, a software update for the TCCM or the vehicle's ECU may resolve communication issues, but this depends on the specific cause of the code.