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P18B5 2017 GMC Sierra Code - Internal Mode Switch 'A' Circuit Shorted

Quick Answer

The P18B5 diagnostic trouble code (DTC) for a 2017 GMC Sierra indicates an issue with the Internal Mode Switch 'A' Circuit being shorted. Common causes include Damaged wiring or connectors in the IMS circuit, Faulty Internal Mode Switch, Corrosion or contamination in the 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
P18B5 2017 GMC Sierra indicates Internal Mode Switch 'A' Circuit Shorted.
Common causes
Common causes include Damaged wiring or connectors in the IMS circuit, Faulty Internal Mode Switch, Corrosion or contamination in the 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 17, 2024
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Code P18B5 2017 GMC Sierra Description

The P18B5 diagnostic trouble code (DTC) for a 2017 GMC Sierra indicates an issue with the Internal Mode Switch 'A' Circuit being shorted. The Internal Mode Switch (IMS) is a component of the transmission system that helps the vehicle's computer determine the current gear selection. When the circuit associated with the IMS is shorted, it means that there is an abnormal connection or low resistance in the circuit, which can disrupt the communication between the transmission control module and the IMS.

OBDII Code P18B5 2017 GMC Sierra - Internal Mode Switch 'A' Circuit Shorted
P18B5 2017 GMC Sierra Code - Internal Mode Switch 'A' Circuit Shorted

Common Causes of P18B5 2017 GMC Sierra

  1. Damaged wiring or connectors in the IMS circuit
  2. Faulty Internal Mode Switch
  3. Corrosion or contamination in the circuit
  4. Electrical issues in the transmission control module
  5. Poor connection or loose wiring in the circuit

Symptoms of P18B5 2017 GMC Sierra

  1. Harsh or delayed shifting
  2. Erratic transmission behavior
  3. Transmission stuck in a single gear
  4. Poor acceleration
  5. Reduced fuel efficiency

How to Fix P18B5 2017 GMC Sierra

  1. Begin by conducting a thorough inspection of the IMS circuit, checking for any visible damage, corrosion, or loose connections.
  2. Test the Internal Mode Switch using a multimeter to determine if it is functioning correctly.
  3. If the IMS is faulty, replace it with a new, OEM-quality component.
  4. Repair or replace any damaged wiring or connectors in the circuit.
  5. Clear the DTC from the vehicle's computer using a diagnostic scan tool and perform a test drive to ensure the issue has been resolved.

Cost to Fix P18B5 2017 GMC Sierra

The typical repair costs for addressing the P18B5 code on a 2017 GMC Sierra can vary depending on the specific cause of the issue and the labor rates in your area. On average, the parts for this repair may cost between $100 and $300, while the labor charges could range from $150 to $400. Keep in mind that these are rough estimates, and actual costs may differ based on the severity of the problem and the rates charged by auto repair shops in your location. It is advisable to obtain quotes from multiple shops to compare prices and ensure you are getting a fair deal.

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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 P18B5 2017 GMC Sierra Code

1. What does OBDII code P18B5 for a 2017 GMC Sierra mean?

The code P18B5 indicates an issue with the Internal Mode Switch 'A' circuit being shorted in the vehicle's transmission control module (TCM).

2. What are the common symptoms of Internal Mode Switch 'A' Circuit Shorted in a 2017 GMC Sierra?

Common symptoms may include erratic shifting behavior, transmission slipping, inability to shift gears properly, and illuminated warning lights on the dashboard.

3. What are the possible causes of OBDII code P18B5 in a 2017 GMC Sierra?

Potential causes of this code may include a faulty internal mode switch, damaged wiring or connectors in the circuit, issues with the TCM, or a short circuit in the system.

4. How can I diagnose the Internal Mode Switch 'A' Circuit Shorted issue in my 2017 GMC Sierra?

Diagnosis typically involves using a scan tool to retrieve the specific trouble code, inspecting the wiring and connectors associated with the internal mode switch, and testing the internal mode switch itself for proper functionality.

5. Is it safe to continue driving my 2017 GMC Sierra with OBDII code P18B5?

It is not recommended to drive the vehicle with this code present, as it can lead to further transmission damage and safety concerns. It is best to address the issue promptly.

6. Can I repair the Internal Mode Switch 'A' Circuit Shorted problem in my 2017 GMC Sierra myself?

While some DIY enthusiasts may attempt to diagnose and repair this issue, it is recommended to seek professional help due to the complexity of transmission systems and the need for specialized equipment.

7. How much does it typically cost to fix OBDII code P18B5 in a 2017 GMC Sierra?

The cost of repair can vary depending on the exact cause of the issue, the extent of the damage, and labor rates in your area. It is advisable to obtain quotes from reputable mechanics or dealerships.

8. Will resetting the trouble codes make the issue go away?

Simply clearing the trouble codes without addressing the underlying problem will not resolve the Internal Mode Switch 'A' Circuit Shorted issue. Proper diagnosis and repair are necessary.

9. Can a low battery voltage trigger code P18B5 in a 2017 GMC Sierra?

Low battery voltage or electrical issues can sometimes cause erroneous fault codes to appear. It is advisable to ensure the battery and charging system are in good condition before proceeding with repairs.

10. How long does it take to fix the Internal Mode Switch 'A' Circuit Shorted problem in a 2017 GMC Sierra?

The repair time can vary depending on the exact cause of the issue, availability of parts, and the technician's expertise. In some cases, it may be a relatively quick fix, while in others, it could take more time for diagnosis and repair.

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