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P18B7 2016 GMC Sierra Code - Internal Mode Switch 'C' Circuit Shorted

Quick Answer

The P18B7 diagnostic trouble code (DTC) for a 2016 GMC Sierra refers to an issue with the Internal Mode Switch 'C' Circuit being shorted. Common causes include Electrical Short: A common cause of a shorted IMS 'C' Circuit is an electrical short within the wiring harness or connections associated with the Internal Mode Switch, This can be due to damaged wiring, corrosion, or a faulty connection, Internal Mode Switch Failure: The IMS itself may be faulty, leading to a short in the 'C' Circuit. 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
P18B7 2016 GMC Sierra indicates Internal Mode Switch 'C' Circuit Shorted.
Common causes
Common causes include Electrical Short: A common cause of a shorted IMS 'C' Circuit is an electrical short within the wiring harness or connections associated with the Internal Mode Switch, This can be due to damaged wiring, corrosion, or a faulty connection, Internal Mode Switch Failure: The IMS itself may be faulty, leading to a short in the 'C' Circuit.
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 07, 2024
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Code P18B7 2016 GMC Sierra Description

The P18B7 diagnostic trouble code (DTC) for a 2016 GMC Sierra refers to an issue with the Internal Mode Switch 'C' Circuit being shorted. The Internal Mode Switch (IMS) is an essential component in the transmission system of the vehicle. It is responsible for providing feedback to the Transmission Control Module (TCM) regarding the position of the transmission gear shift lever. The 'C' Circuit specifically refers to a particular circuit within the IMS that has experienced a short.

OBDII Code P18B7 2016 GMC Sierra - Internal Mode Switch 'C' Circuit Shorted
P18B7 2016 GMC Sierra Code - Internal Mode Switch 'C' Circuit Shorted

Common Causes of P18B7 2016 GMC Sierra

  1. Electrical Short: A common cause of a shorted IMS 'C' Circuit is an electrical short within the wiring harness or connections associated with the Internal Mode Switch. This can be due to damaged wiring, corrosion, or a faulty connection.
  2. Internal Mode Switch Failure: The IMS itself may be faulty, leading to a short in the 'C' Circuit. This can be caused by wear and tear, internal damage, or a manufacturing defect.
  3. Water Intrusion: Water intrusion into the transmission system can cause electrical issues, including shorts in the IMS 'C' Circuit. This can happen due to leaks in the transmission housing or exposure to extreme weather conditions.
  4. Poor Electrical Ground: A poor electrical ground can also lead to issues with the IMS 'C' Circuit, causing a short. This can be due to corrosion or damage to the ground connection.

Symptoms of P18B7 2016 GMC Sierra

  1. Rough Shifting: The vehicle may experience rough or harsh shifting when the IMS 'C' Circuit is shorted.
  2. Transmission Stuck in Gear: The transmission may get stuck in a particular gear and fail to shift properly.
  3. Limp Mode: The vehicle may go into limp mode, restricting performance and speed.
  4. Delayed Shifting: There may be a delay in shifting between gears, leading to hesitation during acceleration.
  5. Warning Lights: The Check Engine Light or Transmission Warning Light may illuminate on the dashboard to indicate a problem with the transmission system.

How to Fix P18B7 2016 GMC Sierra

  1. Diagnostic Testing: The first step in resolving the P18B7 code is to perform diagnostic testing to confirm the issue with the IMS 'C' Circuit.
  2. Inspection: Inspect the wiring harness, connections, and Internal Mode Switch for any signs of damage or wear.
  3. Repair or Replace: Repair any damaged wiring or connections, or replace the Internal Mode Switch if necessary.
  4. Clearing Codes: After making the necessary repairs, clear the DTC and test the vehicle to ensure the issue has been resolved.
  5. Road Test: Take the vehicle for a road test to verify that the transmission is shifting properly and that the code does not return.

Cost to Fix P18B7 2016 GMC Sierra

The cost of repairing a shorted IMS 'C' Circuit can vary depending on the extent of the damage and the specific components that need to be replaced. In general, the cost of parts for this repair can range from $100 to $300, while labor costs may be around $100 to $200. Overall, the total repair cost for addressing the P18B7 DTC in a 2016 GMC Sierra can be estimated to be between $200 and $500. It's important to note that these are rough estimates, and actual costs may vary based on factors such as location, labor rates, and the availability of parts. It is advisable to consult with a qualified mechanic or auto repair shop for a more accurate cost estimate for this repair.

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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 P18B7 2016 GMC Sierra Code

1. What are the common symptoms of OBDII code P18B7 on a 2016 GMC Sierra?

The common symptoms of OBDII code P18B7, which indicates an Internal Mode Switch 'C' Circuit Shorted, may include issues with shifting gears, erratic vehicle speed readings, and illuminated warning lights on the dashboard.

2. What could cause the OBDII code P18B7 to appear on a 2016 GMC Sierra?

The OBDII code P18B7 on a 2016 GMC Sierra is typically triggered by a short circuit in the Internal Mode Switch 'C' circuit. This can be caused by damaged wiring, a faulty internal mode switch, or a poor electrical connection.

3. How can I diagnose the Internal Mode Switch 'C' Circuit Shorted issue on my 2016 GMC Sierra?

To diagnose the Internal Mode Switch 'C' Circuit Shorted problem, you may need to use a diagnostic scanner to retrieve the specific trouble code. Additionally, a thorough visual inspection of the wiring and connections related to the internal mode switch is recommended.

4. Can I continue driving my 2016 GMC Sierra with the OBDII code P18B7 present?

It is not recommended to continue driving your 2016 GMC Sierra with the OBDII code P18B7 present, as it can lead to potential transmission issues and further damage. It is best to address the underlying problem promptly.

5. How can I repair the Internal Mode Switch 'C' Circuit Shorted issue on my 2016 GMC Sierra?

Repairing the Internal Mode Switch 'C' Circuit Shorted problem on a 2016 GMC Sierra may involve replacing the internal mode switch, repairing damaged wiring, or addressing any faulty electrical connections. It is advisable to consult a professional mechanic for proper diagnosis and repair.

6. Is the repair for OBDII code P18B7 on a 2016 GMC Sierra costly?

The cost of repairing the Internal Mode Switch 'C' Circuit Shorted issue on a 2016 GMC Sierra can vary depending on the extent of the damage and the specific components that need to be replaced. It is recommended to obtain quotes from reputable mechanics for an accurate estimate.

7. Can resetting the OBDII code P18B7 on a 2016 GMC Sierra solve the issue temporarily?

Resetting the OBDII code P18B7 on a 2016 GMC Sierra may temporarily clear the fault code, but if the underlying issue causing the Internal Mode Switch 'C' Circuit Shorted problem is not addressed, the code is likely to reappear. It is important to diagnose and repair the root cause of the issue.

8. Are there any safety concerns associated with the OBDII code P18B7 on a 2016 GMC Sierra?

The OBDII code P18B7 indicating an Internal Mode Switch 'C' Circuit Shorted on a 2016 GMC Sierra can pose safety concerns, especially if it affects the transmission's ability to shift gears properly. It is essential to address this issue promptly to ensure safe driving conditions.

9. How long does it typically take to repair the OBDII code P18B7 on a 2016 GMC Sierra?

The repair time for the Internal Mode Switch 'C' Circuit Shorted problem on a 2016 GMC Sierra can vary based on the extent of the damage and the availability of replacement parts. In general, the repair process may take a few hours to complete.

10. Can a DIY enthusiast fix the Internal Mode Switch 'C' Circuit Shorted issue related to OBDII code P18B7 on a 2016 GMC Sierra?

While some DIY enthusiasts may have the skills to address simpler automotive issues, repairing the Internal Mode Switch 'C' Circuit Shorted problem on a 2016 GMC Sierra often requires specialized tools and expertise. For optimal results and safety, it is recommended to seek professional help for this repair.

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