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U135C GMC Code - Lost Communication With Start-Stop Capacitor Control Module

Quick Answer

The U135C GMC code indicates that there is a communication problem with the Start-Stop Capacitor Control Module in the vehicle. Common causes include Faulty Start-Stop Capacitor Control Module: The module itself may be malfunctioning, leading to communication errors, Wiring issues: A damaged or loose wiring connection between the module and other components can disrupt communication, Software glitches: Software issues within the module or the vehicle's system can cause communication breakdowns. 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
U135C GMC indicates Lost Communication With Start-Stop Capacitor Control Module.
Common causes
Common causes include Faulty Start-Stop Capacitor Control Module: The module itself may be malfunctioning, leading to communication errors, Wiring issues: A damaged or loose wiring connection between the module and other components can disrupt communication, Software glitches: Software issues within the module or the vehicle's system can cause communication breakdowns.
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 Aug 19, 2024
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Code U135C GMC Description

The U135C GMC code indicates that there is a communication problem with the Start-Stop Capacitor Control Module in the vehicle. This module is responsible for managing the start-stop system, which automatically shuts off the engine when the vehicle comes to a stop to save fuel and reduce emissions. When this communication is lost, it can lead to issues with the start-stop system not functioning properly, potentially resulting in decreased fuel efficiency and performance.

OBDII Code U135C GMC - Lost Communication With Start-Stop Capacitor Control Module
U135C GMC Code - Lost Communication With Start-Stop Capacitor Control Module

Common Causes of U135C GMC

  1. Faulty Start-Stop Capacitor Control Module: The module itself may be malfunctioning, leading to communication errors.
  2. Wiring issues: A damaged or loose wiring connection between the module and other components can disrupt communication.
  3. Software glitches: Software issues within the module or the vehicle's system can cause communication breakdowns.
  4. Electrical problems: General electrical issues in the vehicle can also affect communication with the module.

Symptoms of U135C GMC

  1. Start-stop system not working: The most obvious symptom is the start-stop system failing to engage or disengage as intended.
  2. Engine stalling: The engine may stall unexpectedly due to communication errors with the capacitor control module.
  3. Warning lights: The vehicle's dashboard may display warning lights related to the start-stop system or communication issues.
  4. Poor fuel efficiency: As the start-stop system may not be functioning correctly, fuel efficiency may be negatively impacted.

How to Fix U135C GMC

  1. Diagnostic scan: Use a diagnostic scan tool to retrieve the specific error codes and pinpoint the issue with the Start-Stop Capacitor Control Module.
  2. Check wiring connections: Inspect the wiring connections to ensure they are secure and free from damage.
  3. Module replacement: If the module is found to be faulty, it may need to be replaced with a new one.
  4. Software update: Updating the software in the module or the vehicle's system may resolve communication issues.
  5. Electrical system check: Conduct a thorough check of the vehicle's electrical system to identify and address any underlying problems.

Cost to Fix U135C GMC

The cost of repairing a lost communication issue with the Start-Stop Capacitor Control Module can vary depending on the specific diagnosis and repair needed. In general, the cost for this type of repair can range from $200 to $500, including parts and labor. However, it's important to note that labor rates can vary significantly between different auto repair shops, so it's recommended to obtain quotes from multiple sources to get an accurate estimate.

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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 U135C GMC Code

1. What does the OBDII code U135C mean on a GMC vehicle?

The U135C code indicates a loss of communication with the Start-Stop Capacitor Control Module, which is part of the vehicle's start-stop system.

2. What are the symptoms of the U135C code?

Common symptoms include a malfunctioning start-stop system, the check engine light or service warning light illuminating, and possible reduced fuel efficiency.

3. What causes the U135C code to appear?

The code can be caused by faulty wiring or connections, a failed Start-Stop Capacitor Control Module, software issues, or problems with the communication network, such as the CAN bus.

4. Can a loose connection cause the U135C code?

Yes, a loose or corroded connection between the Start-Stop Capacitor Control Module and the vehicle's network can trigger this code.

5. How can I diagnose the U135C code?

Diagnose the code by scanning for additional trouble codes, inspecting wiring and connectors for damage or corrosion, and testing the Start-Stop Capacitor Control Module for proper functionality.

6. Is the U135C code related to the battery?

Indirectly, yes. A weak or failing battery can sometimes cause communication issues, including triggering the U135C code.

7. Can I drive with the U135C code?

While the vehicle may still be drivable, the start-stop system may not function correctly, and ignoring the issue could lead to further complications.

8. How do I fix the U135C code on my GMC?

Repairs may involve securing or replacing faulty wiring or connectors, reprogramming or updating software, or replacing the Start-Stop Capacitor Control Module if it’s defective.

9. Is the U135C code covered under warranty?

It depends on your specific GMC warranty. Components like the Start-Stop Capacitor Control Module may be covered under powertrain or emissions warranties.

10. Can a software update resolve the U135C code?

Yes, in some cases, a software update from the manufacturer may resolve communication issues causing the U135C code.

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