AutoCodes – GMC – P18C2 2017 GMC Sierra

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

Quick Answer

The internal mode switch indicates the Transmission Control Module (TCM) which gear position the vehicle operator has selected. Common causes include Faulty Transmission Internal Mode Switch, Transmission Internal Mode Switch harness is open or shorted, Transmission Internal Mode Switch circuit poor electrical connection. 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 Transmission Internal Mode Switch, Transmission Internal Mode Switch harness is open or shorted, Transmission Internal Mode Switch circuit poor electrical connection.
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.

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Code Popularity 182

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 23, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P18C2 2017 GMC Sierra Description

The internal mode switch indicates the Transmission Control Module (TCM) which gear position the vehicle operator has selected. The internal mode switch consists of 5 separate hall effect switches. Each hall effect switch is supplied with a 9 V reference circuit and a signal circuit from the TCM. Each signal circuit for each gear selector position will have either a voltage reading of 0.70-0.96 V indicating On or 1.68-2.38 V indicating Off. The voltage values on each internal mode switch circuit will change and are dependent on the position of the gear selector. The state of each internal mode switch A/B/C/P/S signal circuit is displayed on the scan tool. The Diagnostic Trouble Code (DTC) will be set when the TCM has detected the internal mode switch P signal circuit has an invalid voltage range of 0.70 – 0.96 V for 2.7 s.

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

What does this mean?

What are the Possible Causes of the DTC P18C2 2017 GMC Sierra?

Faulty Transmission Internal Mode Switch
Transmission Internal Mode Switch harness is open or shorted
Transmission Internal Mode Switch circuit poor electrical connection
Faulty Transmission Control Module (TCM)

How to Fix the DTC P18C2 2017 GMC Sierra?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P18C2 2017 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P18C2 2017 GMC Sierra code?

Need more information on how to fix the P18C2 2017 GMC Sierra code? Get Access to Factory Service Manuals

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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.