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U1026 2017 GMC Sierra Code - Lost Communication with Transfer Case Control Module

Quick Answer

The U1026 diagnostic trouble code (DTC) for a 2017 GMC Sierra indicates a communication issue between the vehicle's onboard computer system and the Transfer Case Control Module (TCCM). Common causes include Faulty wiring connections between the vehicle's computer system and the TCCM, Malfunctioning TCCM module, Corrosion or damage to the electrical connectors related to the transfer case system. 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 2017 GMC Sierra indicates Lost Communication with Transfer Case Control Module.
Common causes
Common causes include Faulty wiring connections between the vehicle's computer system and the TCCM, Malfunctioning TCCM module, Corrosion or damage to the electrical connectors related to the transfer case system.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 11, 2024
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Code U1026 2017 GMC Sierra Description

The U1026 diagnostic trouble code (DTC) for a 2017 GMC Sierra indicates a communication issue between the vehicle's onboard computer system and the Transfer Case Control Module (TCCM). The Transfer Case Control Module is responsible for controlling the transfer case, which is the component that allows the vehicle to switch between two-wheel drive and four-wheel drive modes. When communication is lost with the TCCM, it can lead to a variety of issues related to the functionality of the transfer case.

OBDII Code U1026 2017 GMC Sierra - Lost Communication with Transfer Case Control Module
U1026 2017 GMC Sierra Code - Lost Communication with Transfer Case Control Module

Common Causes of U1026 2017 GMC Sierra

  1. Faulty wiring connections between the vehicle's computer system and the TCCM
  2. Malfunctioning TCCM module
  3. Corrosion or damage to the electrical connectors related to the transfer case system
  4. Issues with the vehicle's computer system or software
  5. Environmental factors such as water damage or exposure to moisture

Symptoms of U1026 2017 GMC Sierra

  1. Inability to switch between two-wheel drive and four-wheel drive modes
  2. Dashboard warning lights related to the transfer case system
  3. Unusual noises coming from the transfer case area
  4. Reduced traction or stability in certain driving conditions

How to Fix U1026 2017 GMC Sierra

  1. Diagnose the issue using a diagnostic scan tool to retrieve the DTC and identify the specific communication problem.
  2. Inspect the wiring connections and electrical connectors related to the transfer case system for any signs of damage or corrosion.
  3. Test the TCCM module for functionality and replace if necessary.
  4. Reset the vehicle's computer system and perform a relearn procedure to establish communication with the TCCM.
  5. Clear the DTC and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix U1026 2017 GMC Sierra

The cost of repairing a lost communication issue with the Transfer Case Control Module on a 2017 GMC Sierra can vary depending on the specific cause of the problem. In general, the cost of parts and labor for this repair can range from $200 to $500. This estimate includes the cost of diagnostic testing, replacement parts (such as a new TCCM module or wiring connectors), and labor costs for the repair process. It's important to note that labor rates at auto repair shops can vary, so it's recommended to obtain quotes from several reputable shops to compare costs.

What does this mean?

Tech Notes for U1026 2017 GMC Sierra

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.

Need more information about the U1026 2017 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 2017 GMC Sierra Code

1. What does the OBDII code U1026 mean on a 2017 GMC Sierra?

The U1026 code indicates lost communication with the Transfer Case Control Module (TCCM), meaning the module is not responding or communicating with other vehicle systems.

2. What are the common symptoms of the U1026 code on a 2017 GMC Sierra?

Symptoms may include the 4WD system not engaging, the service 4WD light illuminating, erratic shifting, or no response when selecting 4WD modes.

3. What causes the U1026 code to appear?

Common causes include a faulty Transfer Case Control Module, damaged or corroded wiring or connectors, a blown fuse, or a malfunction in the CAN (Controller Area Network).

4. Can a dead battery trigger the U1026 code on a 2017 GMC Sierra?

Yes, a weak or dead battery can disrupt communication between modules, potentially triggering the U1026 code.

5. How do you diagnose the U1026 code on a 2017 GMC Sierra?

Diagnosis involves checking for other related codes, inspecting the TCCM wiring and connections, testing the CAN network, and verifying the TCCM power supply and ground.

6. Can you drive a 2017 GMC Sierra with the U1026 code?

While it’s possible to drive, the 4WD system may not function properly, which could be risky in certain driving conditions. It’s best to address the issue promptly.

7. How do you fix the U1026 code on a 2017 GMC Sierra?

Repairs may include replacing or repairing damaged wires, cleaning corroded connectors, updating or reprogramming the TCCM, or replacing the faulty module if necessary.

8. Is the U1026 code specific to the 2017 GMC Sierra?

No, the U1026 code is a generic communication code and can appear on other vehicles with similar systems, but the specific symptoms and fixes may vary.

9. Does the U1026 code always mean the TCCM is faulty?

No, most U1026 issues are caused by wiring problems, poor connections, or power supply issues rather than a faulty TCCM itself.

10. How much does it cost to repair the U1026 code on a 2017 GMC Sierra?

Repair costs can vary widely, ranging from $50-$150 for minor wiring repairs to $300-$700 or more if the TCCM needs replacement.

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