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U179A 2018 GMC Sierra Code - Lost Communication with Hybrid/EV Powertrain Control Module 2

Quick Answer

The U179A diagnostic trouble code (DTC) for a 2018 GMC Sierra indicates that there is a communication issue with the Hybrid/EV Powertrain Control Module 2. Common causes include Faulty Hybrid/EV Powertrain Control Module 2, Wiring or connection issues in the communication network, Software glitches or programming errors. 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
U179A 2018 GMC Sierra indicates Lost Communication with Hybrid/EV Powertrain Control Module 2.
Common causes
Common causes include Faulty Hybrid/EV Powertrain Control Module 2, Wiring or connection issues in the communication network, Software glitches or programming errors.
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 12, 2024
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Code U179A 2018 GMC Sierra Description

The U179A diagnostic trouble code (DTC) for a 2018 GMC Sierra indicates that there is a communication issue with the Hybrid/EV Powertrain Control Module 2. This module is responsible for controlling various aspects of the hybrid or electric powertrain system in the vehicle. When communication is lost with this module, it can lead to a range of performance issues and potentially affect the drivability of the vehicle.

OBDII Code U179A 2018 GMC Sierra - Lost Communication with Hybrid/EV Powertrain Control Module 2
U179A 2018 GMC Sierra Code - Lost Communication with Hybrid/EV Powertrain Control Module 2

Common Causes of U179A 2018 GMC Sierra

  1. Faulty Hybrid/EV Powertrain Control Module 2.
  2. Wiring or connection issues in the communication network.
  3. Software glitches or programming errors.
  4. Electrical interference from other components or aftermarket accessories.
  5. Water or moisture intrusion causing corrosion in the module or connections.

Symptoms of U179A 2018 GMC Sierra

  1. Check engine light illuminated on the dashboard.
  2. Loss of hybrid or electric powertrain functionality.
  3. Reduced fuel efficiency.
  4. Engine stalling or hesitation during acceleration.
  5. Inability to switch between hybrid and electric modes.

How to Fix U179A 2018 GMC Sierra

  1. Begin by conducting a thorough inspection of the wiring harness and connections related to the Hybrid/EV Powertrain Control Module 2.
  2. Use a diagnostic scan tool to attempt to establish communication with the module and retrieve any stored fault codes.
  3. If no visible issues are found, try resetting the module by disconnecting the battery for a few minutes and then reconnecting it.
  4. If the problem persists, consider replacing the Hybrid/EV Powertrain Control Module 2 with a new unit and reprogramming it to the vehicle.
  5. After the repair, clear any fault codes and perform a test drive to ensure that the issue has been resolved.

Cost to Fix U179A 2018 GMC Sierra

The cost of repairing a lost communication issue with the Hybrid/EV Powertrain Control Module 2 can vary depending on the specific cause of the problem and the labor rates in your area. On average, you can expect to pay anywhere from $200 to $800 for parts and labor. Keep in mind that diagnostic time and labor rates can vary, so it's recommended to check with local auto repair shops for a more accurate estimate based on your location and vehicle.

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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 U179A 2018 GMC Sierra Code

1. What does the OBDII code U179A mean on a 2018 GMC Sierra?

The U179A code indicates "Lost Communication with Hybrid/EV Powertrain Control Module 2," meaning the vehicle's systems cannot communicate with the secondary powertrain control module.

2. What are the common symptoms of code U179A in a GMC Sierra?

Symptoms may include a check engine light, erratic engine or transmission behavior, reduced power mode, or issues with hybrid/EV system performance.

3. What causes the U179A code to appear in a 2018 GMC Sierra?

Common causes include faulty wiring or connectors, a malfunctioning Hybrid/EV Powertrain Control Module 2, software issues, or a communication bus failure.

4. Can a weak battery trigger the U179A code?

Yes, a weak or failing 12V battery can cause communication errors, including the U179A code, as proper voltage is needed for module communication.

5. How can I diagnose the U179A code on my GMC Sierra?

Diagnose by checking for damaged wiring or loose connections at the Hybrid/EV Powertrain Control Module 2, inspecting the CAN bus network, and using a scan tool to monitor communication.

6. Is it safe to drive with the U179A code active?

It is not recommended to drive with this code active, as it can lead to reduced functionality or failure of the hybrid/EV powertrain system.

7. How much does it cost to fix the U179A code?

Repair costs can vary widely depending on the issue but may range from $100 for wiring repairs to over $1,000 if the control module needs replacement.

8. Can updating the vehicle’s software resolve the U179A code?

Yes, in some cases, a software update or reprogramming of the powertrain control module can resolve communication issues.

9. What tools are needed to fix the U179A code?

You’ll need an advanced scan tool capable of reading and diagnosing communication faults, as well as basic tools to inspect wiring and connectors.

10. Can a short circuit cause the U179A code?

Yes, a short circuit in the wiring harness or connectors can disrupt communication and trigger the U179A code.

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