AutoCodes – GMC – P18C2 2015 GMC Sierra

P18C2 2015 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 2015 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 187

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
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code P18C2 2015 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 2015 GMC Sierra - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range - AutoCodes.com — P18C2 2015 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 2015 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 2015 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 2015 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 2015 GMC Sierra code?

Need more information on how to fix the P18C2 2015 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P18C2 2015 GMC Sierra code diagnosed by a professional: Find a repair shop in your area

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 2015 GMC Sierra Code

1. What are the common symptoms of OBDII code P18C2 in a 2015 GMC Sierra?

The common symptoms of OBDII code P18C2, Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range, in a 2015 GMC Sierra may include issues with shifting gears, the transmission not responding correctly, or the vehicle going into a limp mode.

2. What are the possible causes of OBDII code P18C2 in a 2015 GMC Sierra?

The possible causes of OBDII code P18C2 in a 2015 GMC Sierra include a faulty internal mode switch, damaged wiring or connectors in the internal mode switch circuit, or an issue with the transmission control module.

3. How can I diagnose OBDII code P18C2 in a 2015 GMC Sierra?

Diagnosing OBDII code P18C2 in a 2015 GMC Sierra involves using a scan tool to retrieve the code, inspecting the internal mode switch and its wiring for any visible damage, and testing the voltage range of the internal mode switch circuit.

4. Can I continue driving my 2015 GMC Sierra with OBDII code P18C2?

It is not recommended to continue driving your 2015 GMC Sierra with OBDII code P18C2, as it can lead to further damage to the transmission and other components. It is best to address the issue promptly to avoid costly repairs.

5. How can I repair OBDII code P18C2 in a 2015 GMC Sierra?

Repairing OBDII code P18C2 in a 2015 GMC Sierra may involve replacing the internal mode switch, repairing or replacing damaged wiring or connectors, or reprogramming the transmission control module. It is advisable to consult a professional mechanic for an accurate diagnosis and repair.

6. Is OBDII code P18C2 a common issue in 2015 GMC Sierra vehicles?

While OBDII code P18C2, Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range, may not be extremely common in 2015 GMC Sierra vehicles, it can still occur due to various factors like wear and tear or electrical issues.

7. Can a DIY enthusiast fix OBDII code P18C2 in a 2015 GMC Sierra?

While some DIY enthusiasts may have the skills to address OBDII code P18C2 in a 2015 GMC Sierra, due to the complexity of transmission-related issues, it is generally recommended to seek professional help to ensure proper diagnosis and repair.

8. Will resetting the OBDII code P18C2 in a 2015 GMC Sierra make it go away permanently?

Simply resetting the OBDII code P18C2 in a 2015 GMC Sierra may temporarily clear the code, but if the underlying issue causing the code is not addressed, it is likely to reappear. It is crucial to diagnose and repair the root cause of the problem.

9. How much does it cost to fix OBDII code P18C2 in a 2015 GMC Sierra?

The cost to fix OBDII code P18C2 in a 2015 GMC Sierra can vary depending on the exact cause of the issue, labor rates in your area, and whether you choose OEM or aftermarket parts. It is advisable to obtain quotes from reputable mechanics for an accurate estimate.

10. Can OBDII code P18C2 in a 2015 GMC Sierra cause permanent damage if left unresolved?

If OBDII code P18C2, Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range, in a 2015 GMC Sierra is left unresolved, it can potentially cause permanent damage to the transmission and other related components. It is best to address the issue promptly to prevent further damage.