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Engine-Codes – GMC – C1118 GMC

C1118 GMC Code - Trailer Brake Control Sensitivity Switch Circuit Malfunction

Quick Answer

The C1118 GMC code indicates a Trailer Brake Control Sensitivity Switch Circuit Malfunction. Common causes include Damaged wiring or connectors in the sensitivity switch circuit, Faulty sensitivity switch, Issues with the trailer brake control module. 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
C1118 GMC indicates Trailer Brake Control Sensitivity Switch Circuit Malfunction.
Common causes
Common causes include Damaged wiring or connectors in the sensitivity switch circuit, Faulty sensitivity switch, Issues with the trailer brake control module.
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 17, 2024
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Code C1118 GMC Description

The C1118 GMC code indicates a Trailer Brake Control Sensitivity Switch Circuit Malfunction. This means that there is an issue with the sensitivity switch circuit that controls the trailer brake system in the vehicle. The trailer brake control system is responsible for applying the brakes on a trailer when the vehicle's brakes are applied, ensuring safe and smooth towing. When this circuit malfunctions, it can lead to issues with the trailer brake system, affecting the vehicle's ability to tow trailers safely.

OBDII Code C1118 GMC - Trailer Brake Control Sensitivity Switch Circuit Malfunction
C1118 GMC Code - Trailer Brake Control Sensitivity Switch Circuit Malfunction

Common Causes of C1118 GMC

  1. Damaged wiring or connectors in the sensitivity switch circuit
  2. Faulty sensitivity switch
  3. Issues with the trailer brake control module
  4. Corrosion or moisture in the trailer brake system components
  5. Electrical issues in the vehicle's wiring system

Symptoms of C1118 GMC

  1. Erratic trailer brake operation
  2. Dashboard warning lights related to the trailer brake system
  3. Inconsistent braking performance while towing
  4. Difficulty applying brakes smoothly when towing a trailer

How to Fix C1118 GMC

  1. Begin by conducting a thorough inspection of the sensitivity switch circuit, checking for any visible damage to the wiring or connectors.
  2. Test the sensitivity switch to determine if it is functioning correctly or needs replacement.
  3. Check the trailer brake control module for any faults or malfunctions, and replace if necessary.
  4. Clear the diagnostic trouble codes from the vehicle's system to reset the trailer brake control sensitivity switch circuit.
  5. Test the trailer brake system to ensure that the issue has been resolved and that the brakes are operating smoothly and effectively while towing.

Cost to Fix C1118 GMC

The typical repair costs for addressing a Trailer Brake Control Sensitivity Switch Circuit Malfunction can range from $200 to $500, including parts and labor. However, it's important to note that the specific diagnosis time and labor rates at auto repair shops can vary based on factors such as location, vehicle make and model, and engine type. Rates in metropolitan areas or at dealerships may be higher, while independent shops often charge less. It's recommended to check local rates for a more accurate estimate before proceeding with the repair.

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Information for Specific GMC Models

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 C1118 GMC Code

1. What are the common symptoms of OBDII code C1118 GMC (Trailer Brake Control Sensitivity Switch Circuit Malfunction)?

The common symptoms include issues with the trailer brake system, such as erratic braking, non-responsive brakes, or the trailer brakes engaging unexpectedly.

2. What can cause the OBDII code C1118 GMC to trigger?

This code is typically triggered by a malfunction in the sensitivity switch circuit of the trailer brake control system. It can be caused by wiring issues, a faulty sensitivity switch, or problems with the trailer brake control module.

3. How can I diagnose the cause of OBDII code C1118 GMC?

Diagnosing this code involves checking the wiring connections, testing the sensitivity switch for proper functioning, and using a scan tool to communicate with the trailer brake control module for any stored codes or data.

4. Are there any repair tips for fixing OBDII code C1118 GMC?

Repairing this code may involve repairing or replacing damaged wiring, replacing the sensitivity switch, or reprogramming the trailer brake control module. It's essential to follow manufacturer-specific repair procedures for proper troubleshooting and repair.

5. Can I still drive my vehicle with OBDII code C1118 GMC present?

It is not recommended to drive the vehicle with this code present, especially if it affects the trailer brake system. Addressing the issue promptly is crucial for the safety and proper functioning of the trailer brakes.

6. How serious is OBDII code C1118 GMC?

While this code may not affect the drivability of the vehicle itself, it can impact the functionality of the trailer brake system, which is crucial for towing safety. It should be addressed promptly to avoid any potential safety hazards.

7. Can I reset OBDII code C1118 GMC with a simple reset tool?

While you may be able to clear the code temporarily with a reset tool, it is essential to diagnose and repair the underlying issue causing the code to prevent it from reoccurring.

8. How much does it typically cost to repair OBDII code C1118 GMC?

The cost of repairing this code can vary depending on the cause of the issue, the labor rates in your area, and the specific parts needed for the repair. It's recommended to obtain quotes from automotive professionals for an accurate estimate.

9. Is OBDII code C1118 GMC specific to certain GMC models?

This code is specific to GMC vehicles equipped with a trailer brake control system. It may be found in various GMC models that have this feature installed.

10. Can I prevent OBDII code C1118 GMC from occurring in the future?

Regular maintenance of the trailer brake system, including checking the wiring connections and ensuring proper functioning of the sensitivity switch, can help prevent this code from occurring in the future.

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