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P18B5 2016 GMC Sierra Code - Internal Mode Switch 'A' Circuit Shorted

Quick Answer

The P18B5 diagnostic trouble code (DTC) for a 2016 GMC Sierra indicates an issue with the Internal Mode Switch 'A' Circuit being shorted. Common causes include Wiring harness damage, Corrosion or loose connections in the IMS circuit, Faulty 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
P18B5 2016 GMC Sierra indicates Internal Mode Switch 'A' Circuit Shorted.
Common causes
Common causes include Wiring harness damage, Corrosion or loose connections in the IMS circuit, Faulty 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 15, 2024
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Code P18B5 2016 GMC Sierra Description

The P18B5 diagnostic trouble code (DTC) for a 2016 GMC Sierra indicates an issue with the Internal Mode Switch 'A' Circuit being shorted. The Internal Mode Switch (IMS) is a component within the transmission control module that is responsible for providing feedback to the vehicle's computer regarding the gear selection made by the driver. When the IMS 'A' circuit is shorted, it means that there is an electrical fault in the circuit that is preventing the proper communication between the IMS and the transmission control module.

OBDII Code P18B5 2016 GMC Sierra - Internal Mode Switch 'A' Circuit Shorted
P18B5 2016 GMC Sierra Code - Internal Mode Switch 'A' Circuit Shorted

Common Causes of P18B5 2016 GMC Sierra

  1. Wiring harness damage
  2. Corrosion or loose connections in the IMS circuit
  3. Faulty IMS sensor
  4. Issues with the transmission control module

Symptoms of P18B5 2016 GMC Sierra

  1. Erratic shifting behavior
  2. Transmission slippage
  3. Harsh shifts
  4. Transmission stuck in a single gear
  5. Limp mode activation

How to Fix P18B5 2016 GMC Sierra

  1. Begin by conducting a thorough inspection of the wiring harness and connections in the IMS circuit to identify any damage or corrosion.
  2. Test the IMS sensor for proper functionality using a multimeter to check for continuity and resistance.
  3. If the IMS sensor is faulty, replace it with a new one following the manufacturer's guidelines.
  4. Clear the DTC from the vehicle's computer using a scan tool and test drive the vehicle to ensure that the issue has been resolved.
  5. If the problem persists, further diagnostics may be required to identify any underlying issues with the transmission control module.

Cost to Fix P18B5 2016 GMC Sierra

The typical repair costs for addressing a shorted IMS 'A' circuit can range from $200 to $500, including parts and labor. However, it's important to note that the specific diagnosis time and labor rates at auto repair shops can vary based on factors such as location, vehicle make and model, and engine type. Rates in metropolitan areas or at dealerships may be higher, while independent shops often charge less. It's advisable to check local rates for a more precise estimate.

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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 2016 GMC Sierra Code

1. What are the common symptoms of OBDII code P18B5 on a 2016 GMC Sierra?

The common symptoms of OBDII code P18B5, which indicates an Internal Mode Switch 'A' Circuit Shorted, may include difficulty shifting gears, erratic shifting behavior, and possibly illumination of the check engine light.

2. What are some possible causes of OBDII code P18B5 on a 2016 GMC Sierra?

Possible causes of OBDII code P18B5 on a 2016 GMC Sierra include a faulty internal mode switch, damaged wiring or connectors related to the switch, or an internal fault within the transmission control module.

3. How can I diagnose OBDII code P18B5 on my 2016 GMC Sierra?

Diagnosing OBDII code P18B5 may involve using a scan tool to retrieve the code, inspecting the internal mode switch and its wiring for damage, and testing the switch for proper functionality. It is recommended to consult a professional mechanic for accurate diagnosis.

4. Can I continue to drive my 2016 GMC Sierra with OBDII code P18B5 present?

It is not recommended to continue driving your 2016 GMC Sierra with OBDII code P18B5 present, as it can lead to further damage to the transmission or other components. It is best to address the issue promptly to avoid potential safety hazards.

5. How can OBDII code P18B5 on a 2016 GMC Sierra be repaired?

Repairing OBDII code P18B5 may involve replacing the internal mode switch, repairing or replacing damaged wiring or connectors, or reprogramming the transmission control module. It is advisable to have the repairs done by a qualified technician.

6. Is it possible to reset OBDII code P18B5 on a 2016 GMC Sierra without fixing the underlying issue?

While you can clear the code temporarily using a scan tool, it will likely reappear if the underlying issue causing OBDII code P18B5 is not addressed. It is essential to fix the problem to prevent further complications.

7. How much does it typically cost to repair OBDII code P18B5 on a 2016 GMC Sierra?

The cost of repairing OBDII code P18B5 on a 2016 GMC Sierra can vary depending on the exact cause of the issue, labor rates in your area, and the cost of parts. It is best to obtain a diagnosis and repair estimate from a reputable repair shop.

8. Can a DIY enthusiast fix OBDII code P18B5 on a 2016 GMC Sierra?

While some experienced DIY enthusiasts may be able to diagnose and repair OBDII code P18B5, it is a complex issue related to the transmission system. It is recommended to seek professional help to ensure proper diagnosis and repair.

9. Will OBDII code P18B5 cause permanent damage to my 2016 GMC Sierra if left unresolved?

Leaving OBDII code P18B5 unresolved can potentially cause further damage to the transmission or other components over time. It is best to address the issue promptly to prevent costly repairs or safety risks.

10. How long does it typically take to repair OBDII code P18B5 on a 2016 GMC Sierra?

The repair time for OBDII code P18B5 on a 2016 GMC Sierra can vary depending on the exact cause of the issue and the availability of parts. It is advisable to consult with a mechanic for an accurate estimate of the repair timeline.

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