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P18B6 2014 GMC Sierra Code - Internal Mode Switch 'B' Circuit Shorted

Quick Answer

The P18B6 diagnostic trouble code (DTC) for a 2014 GMC Sierra indicates that there is a short circuit in the internal mode switch 'B' circuit. Common causes include Wiring or connector issues in the internal mode switch 'B' circuit, Internal mode switch failure, TCM malfunction. 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
P18B6 2014 GMC Sierra indicates Internal Mode Switch 'B' Circuit Shorted.
Common causes
Common causes include Wiring or connector issues in the internal mode switch 'B' circuit, Internal mode switch failure, TCM malfunction.
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 15, 2024
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Code P18B6 2014 GMC Sierra Description

The P18B6 diagnostic trouble code (DTC) for a 2014 GMC Sierra indicates that there is a short circuit in the internal mode switch 'B' circuit. The internal mode switch is a component of the transmission control module (TCM) that helps the vehicle's computer determine the gear position of the transmission. When the internal mode switch 'B' circuit is shorted, it can lead to incorrect gear selection, erratic shifting behavior, and potential safety hazards.

OBDII Code P18B6 2014 GMC Sierra - Internal Mode Switch 'B' Circuit Shorted
P18B6 2014 GMC Sierra Code - Internal Mode Switch 'B' Circuit Shorted

Common Causes of P18B6 2014 GMC Sierra

  1. Wiring or connector issues in the internal mode switch 'B' circuit
  2. Internal mode switch failure
  3. TCM malfunction
  4. Electrical interference or shorts in the transmission control system
  5. Water or corrosion damage to the internal mode switch or its connections

Symptoms of P18B6 2014 GMC Sierra

  1. Harsh or erratic shifting
  2. Delayed engagement when shifting gears
  3. Transmission slipping
  4. Inability to shift into certain gears
  5. Illumination of the check engine light

How to Fix P18B6 2014 GMC Sierra

  1. Begin by conducting a thorough inspection of the internal mode switch 'B' circuit, checking for any visible damage to wiring or connectors.
  2. Test the internal mode switch for proper functionality using a multimeter or diagnostic tool to determine if it is shorted or malfunctioning.
  3. If the internal mode switch is faulty, replace it with a new component following manufacturer guidelines.
  4. Clear the DTC from the vehicle's computer using a diagnostic tool to reset the system and ensure the issue has been resolved.
  5. Test drive the vehicle to confirm that the transmission is operating correctly and that the symptoms associated with the P18B6 code have been eliminated.

Cost to Fix P18B6 2014 GMC Sierra

The typical repair costs for addressing the P18B6 code on a 2014 GMC Sierra can vary depending on the specific cause of the issue and the extent of the repairs needed. In general, replacing the internal mode switch or addressing wiring/connectivity issues may cost between $200 and $500, including parts and labor. However, it is essential to note that diagnosis time and labor rates at auto repair shops can vary significantly based on factors such as location, vehicle make and model, and engine type. Rates typically range between $80 and $150 per hour, with higher rates in metropolitan areas or at dealerships and lower rates at independent shops. For a more precise estimate, it is advisable to consult with local auto repair shops.

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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 P18B6 2014 GMC Sierra Code

1. What are the common symptoms of OBDII code P18B6 ('Internal Mode Switch 'B' Circuit Shorted') in a 2014 GMC Sierra?

The common symptoms include issues with shifting gears, difficulty engaging or disengaging gears, and the transmission not responding properly to driver input.

2. What are the possible causes of the Internal Mode Switch 'B' Circuit Shorted code in a 2014 GMC Sierra?

Possible causes include a faulty internal mode switch, damaged wiring or connectors in the circuit, a short circuit in the internal mode switch circuit, or a malfunctioning transmission control module.

3. How can I diagnose OBDII code P18B6 in my 2014 GMC Sierra?

Diagnosing this code typically involves using a scan tool to retrieve the trouble codes, inspecting the internal mode switch and its circuit for damage, and testing the wiring and connectors for continuity and proper voltage.

4. Can I continue driving my 2014 GMC Sierra with the Internal Mode Switch 'B' Circuit Shorted code?

It is not recommended to drive the vehicle with this code present, as it can lead to further transmission issues and potentially cause unsafe driving conditions. It's best to address the problem promptly.

5. Are there any DIY repair tips for fixing OBDII code P18B6 in a 2014 GMC Sierra?

DIY repair tips include checking the internal mode switch for proper operation, inspecting the wiring and connectors for damage, and ensuring all connections are secure. However, complex repairs may require professional assistance.

6. How much does it typically cost to repair OBDII code P18B6 in a 2014 GMC Sierra?

The cost of repairing this code can vary depending on the specific issue causing it. Simple fixes like replacing a damaged connector may be relatively inexpensive, while more complex repairs involving the transmission control module can be costly.

7. Can resetting the OBDII code P18B6 in a 2014 GMC Sierra make it go away permanently?

Resetting the code may temporarily clear the error code, but if the underlying issue causing the code is not fixed, it is likely to return. It's important to diagnose and repair the problem to prevent future occurrences.

8. How urgent is it to address OBDII code P18B6 ('Internal Mode Switch 'B' Circuit Shorted') in a 2014 GMC Sierra?

It is recommended to address this code promptly to prevent further transmission issues and potential safety hazards while driving. Ignoring the code can lead to more significant problems down the line.

9. Will OBDII code P18B6 in a 2014 GMC Sierra cause the vehicle to go into a "limp mode"?

Yes, in some cases, this code can cause the vehicle to go into a limp mode to protect the transmission from further damage. This mode limits the vehicle's performance to prevent additional issues.

10. Can a faulty battery or alternator cause OBDII code P18B6 in a 2014 GMC Sierra?

While a faulty battery or alternator may cause electrical issues in a vehicle, they are not common causes of the Internal Mode Switch 'B' Circuit Shorted code. It is more likely related to the internal mode switch, wiring, or transmission control module.

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