AutoCodes – GMC – P18C2 2016 GMC Sierra

P18C2 2016 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 2016 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 325

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 2016 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 2016 GMC Sierra - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range - AutoCodes.com — P18C2 2016 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 2016 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 2016 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 2016 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 2016 GMC Sierra code?

Need more information on how to fix the P18C2 2016 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P18C2 2016 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 2016 GMC Sierra Code

1. What are the common symptoms of OBDII code P18C2 in a 2016 GMC Sierra?

The common symptoms of OBDII code P18C2 in a 2016 GMC Sierra include issues with gear shifting, the vehicle getting stuck in a particular gear, or the transmission not engaging properly.

2. What can cause the Internal Mode Switch 'P' Circuit to be stuck on an invalid voltage range in a 2016 GMC Sierra?

Causes of the Internal Mode Switch 'P' Circuit stuck on an invalid voltage range in a 2016 GMC Sierra can include a faulty internal mode switch, damaged wiring or connectors, or issues with the transmission control module.

3. How serious is the OBDII code P18C2 in a 2016 GMC Sierra?

The OBDII code P18C2 indicating the Internal Mode Switch 'P' Circuit stuck on an invalid voltage range in a 2016 GMC Sierra is a serious issue as it can affect the proper functioning of the transmission and lead to driving safety concerns.

4. Can I continue driving my 2016 GMC Sierra with the OBDII code P18C2?

It is not recommended to continue driving your 2016 GMC Sierra with the OBDII code P18C2 as it can result in further damage to the transmission components and potentially cause unsafe driving conditions.

5. How can I diagnose and repair OBDII code P18C2 in a 2016 GMC Sierra?

Diagnosing and repairing OBDII code P18C2 in a 2016 GMC Sierra requires a thorough inspection of the internal mode switch, wiring, connectors, and transmission control module. It is recommended to seek professional help for accurate diagnosis and proper repair.

6. Can resetting the OBDII system clear the P18C2 code in a 2016 GMC Sierra?

Resetting the OBDII system may temporarily clear the P18C2 code in a 2016 GMC Sierra, but if the underlying issue causing the code is not addressed, it is likely to reappear. It is important to diagnose and fix the root cause of the problem.

7. How much does it typically cost to repair OBDII code P18C2 in a 2016 GMC Sierra?

The cost of repairing OBDII code P18C2 in a 2016 GMC Sierra can vary depending on the exact cause of the issue, parts needed for replacement, and labor costs. It is advisable to get a professional diagnosis and estimate for an accurate cost assessment.

8. Is the Internal Mode Switch 'P' Circuit stuck on an invalid voltage range covered under warranty for a 2016 GMC Sierra?

The coverage of the Internal Mode Switch 'P' Circuit issue under warranty for a 2016 GMC Sierra depends on factors like the vehicle's warranty status, mileage, and the specific terms and conditions of the warranty. Check with your dealership or manufacturer for warranty eligibility.

9. Can a DIY enthusiast fix the Internal Mode Switch 'P' Circuit issue causing OBDII code P18C2 in a 2016 GMC Sierra?

While some experienced DIY enthusiasts may have the skills to diagnose and repair the Internal Mode Switch 'P' Circuit issue causing OBDII code P18C2 in a 2016 GMC Sierra, it is generally recommended to seek professional help due to the complexity of transmission-related repairs.

10. Are there any preventive measures to avoid OBDII code P18C2 in a 2016 GMC Sierra?

Routine maintenance, such as checking and servicing the transmission components, inspecting wiring and connectors for damage, and addressing any issues promptly, can help prevent the occurrence of the Internal Mode Switch 'P' Circuit problem leading to OBDII code P18C2 in a 2016 GMC Sierra.