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P18C2 2016 GMC Sierra Code - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range

Quick Answer

The diagnostic trouble code P18C2 for a 2016 GMC Sierra refers to the Internal Mode Switch 'P' Circuit being stuck on an invalid voltage range. Common causes include Faulty Internal Mode Switch (IMS) sensor, Wiring issues or damaged connectors related to the IMS circuit, Corrosion or water intrusion in the IMS sensor. 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 Internal Mode Switch (IMS) sensor, Wiring issues or damaged connectors related to the IMS circuit, Corrosion or water intrusion in the IMS sensor.
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 11, 2024
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Code P18C2 2016 GMC Sierra Description

The diagnostic trouble code P18C2 for a 2016 GMC Sierra refers to the Internal Mode Switch 'P' Circuit being stuck on an invalid voltage range. In modern vehicles, the Internal Mode Switch (IMS) is an essential component that communicates the gear selector position to the vehicle's electronic control unit (ECU) or transmission control module (TCM). The 'P' circuit specifically refers to the park position on the gear selector.

OBDII Code P18C2 2016 GMC Sierra - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range
P18C2 2016 GMC Sierra Code - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range

Common Causes of P18C2 2016 GMC Sierra

  1. Faulty Internal Mode Switch (IMS) sensor.
  2. Wiring issues or damaged connectors related to the IMS circuit.
  3. Corrosion or water intrusion in the IMS sensor.
  4. ECU or TCM software glitches or malfunctions.
  5. Electrical issues such as a weak battery or alternator.

Symptoms of P18C2 2016 GMC Sierra

  1. Difficulty shifting gears or selecting the park position.
  2. Inaccurate gear indicator display on the instrument cluster.
  3. Transmission slipping or jerking during acceleration or deceleration.
  4. Vehicle not starting or engaging in gear properly.
  5. Check Engine Light (CEL) illuminated on the dashboard.

How to Fix P18C2 2016 GMC Sierra

  1. Diagnose the issue using a professional diagnostic scan tool to confirm the P18C2 code and pinpoint the exact cause.
  2. Inspect the Internal Mode Switch (IMS) sensor and its wiring for any visible damage or corrosion. Replace the sensor if necessary.
  3. Check the ECU or TCM for any software updates or glitches. Perform a reflash or reset if required.
  4. Test the voltage output of the IMS circuit to ensure it falls within the correct range. Repair or replace any faulty wiring or connectors.
  5. Clear the trouble code from the vehicle's ECU memory and perform a test drive to verify that the issue has been resolved.

Cost to Fix P18C2 2016 GMC Sierra

The typical repair costs for addressing the P18C2 code on a 2016 GMC Sierra can vary depending on the specific cause of the issue. On average, the parts for replacing the Internal Mode Switch (IMS) sensor may range from $50 to $150, while labor costs can add another $100 to $200. Overall, the total repair cost could amount to around $150 to $350, excluding any additional diagnostic fees or taxes.

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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 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.

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