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P18C2 2017 GMC Sierra Code - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range

Quick Answer

The diagnostic trouble code P18C2 for a 2017 GMC Sierra indicates an issue with the Internal Mode Switch 'P' Circuit being stuck on an invalid voltage range. Common causes include Faulty Internal Mode Switch, Damaged wiring or connectors in the circuit, Malfunctioning transmission 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
P18C2 2017 GMC Sierra indicates Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range.
Common causes
Common causes include Faulty Internal Mode Switch, Damaged wiring or connectors in the circuit, Malfunctioning transmission 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 16, 2024
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Code P18C2 2017 GMC Sierra Description

The diagnostic trouble code P18C2 for a 2017 GMC Sierra indicates an issue with the Internal Mode Switch 'P' Circuit being stuck on an invalid voltage range. The Internal Mode Switch (IMS) is a component in the transmission system that helps the vehicle's computer determine the current gear selection. When the circuit associated with the IMS is stuck on an invalid voltage range, it means that the voltage signal being sent to the vehicle's computer is outside of the expected parameters. This can lead to incorrect gear selection, transmission shifting issues, and potential safety concerns.

OBDII Code P18C2 2017 GMC Sierra - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range
P18C2 2017 GMC Sierra Code - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range

Common Causes of P18C2 2017 GMC Sierra

  1. Faulty Internal Mode Switch
  2. Damaged wiring or connectors in the circuit
  3. Malfunctioning transmission control module
  4. Issues with the vehicle's computer system
  5. Corrosion or water damage in the transmission system components

Symptoms of P18C2 2017 GMC Sierra

  1. Incorrect gear selection displayed on the dashboard
  2. Transmission shifting erratically or slipping
  3. Harsh gear changes during acceleration or deceleration
  4. Check Engine Light illuminated on the dashboard

How to Fix P18C2 2017 GMC Sierra

  1. Diagnose the issue using a diagnostic scanner to retrieve the specific trouble code and pinpoint the root cause.
  2. Inspect the Internal Mode Switch, wiring, and connectors for any visible damage or corrosion.
  3. Test the voltage output of the Internal Mode Switch to determine if it falls within the acceptable range.
  4. Replace the Internal Mode Switch if it is found to be faulty, and repair any damaged wiring or connectors.
  5. Clear the trouble code from the vehicle's computer memory and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P18C2 2017 GMC Sierra

The typical repair costs for addressing the Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range code can vary depending on the extent of the damage and the specific components that need to be replaced. In general, the cost of replacing the Internal Mode Switch and repairing any wiring issues can range from $200 to $500, including parts and labor. However, it's important to note that the actual cost can be higher or lower based on the factors mentioned earlier. It's recommended to consult with a trusted auto repair shop for a more accurate estimate based on your vehicle's make and model.

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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 P18C2 2017 GMC Sierra Code

1. What are the common symptoms of OBDII code P18C2 in a 2017 GMC Sierra?

The common symptoms of OBDII code P18C2 include issues with shifting gears, the vehicle getting stuck in a particular gear, and the inability to start the vehicle.

2. What are the possible causes of the Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range fault code in a 2017 GMC Sierra?

Possible causes of the P18C2 code in a 2017 GMC Sierra include a faulty internal mode switch, damaged wiring or connectors, or issues with the transmission control module.

3. How can I diagnose the Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range issue in my 2017 GMC Sierra?

Diagnosing the P18C2 code may involve checking the internal mode switch for proper operation, inspecting the wiring and connectors for any damage, and using a diagnostic scanner to retrieve trouble codes.

4. Is it safe to continue driving my 2017 GMC Sierra with OBDII code P18C2 present?

It is not recommended to continue driving your vehicle with the P18C2 code as it can lead to further transmission issues and potentially cause damage. It's best to address the problem promptly.

5. How can I repair the Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range fault code in my 2017 GMC Sierra?

Repairing the P18C2 code may involve replacing the internal mode switch, repairing or replacing damaged wiring or connectors, and resetting the trouble codes using a diagnostic tool.

6. Can a DIY enthusiast fix the P18C2 code in a 2017 GMC Sierra?

While some aspects of diagnosing and repairing the P18C2 code may be within reach for DIY enthusiasts, it is recommended to consult with a professional mechanic for accurate diagnosis and proper repair.

7. Will resetting the OBDII code P18C2 in my 2017 GMC Sierra make it go away permanently?

Resetting the P18C2 code may clear it temporarily, but if the underlying issue is not addressed, the code is likely to reappear. It's crucial to diagnose and repair the root cause of the problem.

8. How long does it typically take to repair the Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range fault in a 2017 GMC Sierra?

The repair time for the P18C2 code can vary depending on the exact cause of the issue and the complexity of the repair. It may take anywhere from a couple of hours to a full day in some cases.

9. Can extreme weather conditions affect the occurrence of OBDII code P18C2 in a 2017 GMC Sierra?

Extreme weather conditions can potentially exacerbate existing issues that lead to the P18C2 code, such as electrical connections becoming compromised or damaged. It's important to keep this in mind when diagnosing the problem.

10. Are there any preventive measures to avoid encountering the Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range fault code in a 2017 GMC Sierra?

Regular maintenance checks, keeping an eye on transmission performance, and addressing any issues promptly can help prevent the occurrence of the P18C2 code in your 2017 GMC Sierra.

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