Engine-CodesGMC – P18B8 2017 GMC Sierra

P18B8 2017 GMC Sierra Code - Internal Mode Switch 'P' Circuit Shorted

Quick Answer

The diagnostic trouble code P18B8 for a 2017 GMC Sierra indicates an issue with the Internal Mode Switch 'P' Circuit being shorted. Common causes include Faulty Internal Mode Switch, Wiring issues, Corrosion in electrical connections. 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
P18B8 2017 GMC Sierra indicates Internal Mode Switch 'P' Circuit Shorted.
Common causes
Common causes include Faulty Internal Mode Switch, Wiring issues, Corrosion in electrical connections.
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.
Table of contents Created and updated by William Orellana on Sep 13, 2024
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Code P18B8 2017 GMC Sierra Description

The diagnostic trouble code P18B8 for a 2017 GMC Sierra indicates an issue with the Internal Mode Switch 'P' 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 'P' circuit is shorted, it means that there is an electrical problem within the IMS that is preventing it from properly communicating with the vehicle's computer.

OBDII Code P18B8 2017 GMC Sierra - Internal Mode Switch 'P' Circuit Shorted
P18B8 2017 GMC Sierra Code - Internal Mode Switch 'P' Circuit Shorted

Common Causes of P18B8 2017 GMC Sierra

  1. Faulty Internal Mode Switch
  2. Wiring issues
  3. Corrosion in electrical connections
  4. Problems with the vehicle's computer system

Symptoms of P18B8 2017 GMC Sierra

  1. Rough shifting
  2. Hesitation when accelerating
  3. Transmission getting stuck in a gear
  4. Limp mode activation

How to Fix P18B8 2017 GMC Sierra

  1. Diagnose the issue by using a scan tool to check for the specific fault code and inspecting the IMS and related wiring.
  2. Replace the Internal Mode Switch if it is found to be faulty.
  3. Repair any damaged wiring or connectors.
  4. Clear the fault code from the vehicle's computer system and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P18B8 2017 GMC Sierra

The typical repair costs for addressing a P18B8 code on a 2017 GMC Sierra 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. Most auto repair shops commonly charge between $80 and $150 per hour; however, 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 P18B8 2017 GMC Sierra Code

What does the OBDII code P18B8 mean for a 2017 GMC Sierra?

The code P18B8 indicates an issue with the Internal Mode Switch 'P' Circuit, specifically a shorted condition in the circuit.

What are common symptoms of the P18B8 code in a GMC Sierra?

Common symptoms include difficulty shifting into Park, the transmission failing to recognize the Park position, or the vehicle not starting properly.

What causes the P18B8 code to appear?

The code is typically triggered by wiring issues, such as a short circuit, damaged connectors, or a faulty internal mode switch within the transmission.

Can the P18B8 code affect drivability?

Yes, it can affect drivability by preventing the vehicle from shifting into Park properly, which may compromise safety and functionality.

How is the P18B8 code diagnosed?

A mechanic will use a scan tool to read the code, inspect the wiring and connectors for damage, and test the internal mode switch for proper operation.

Can I drive with the P18B8 code active?

It is not recommended, as issues with the Park circuit can pose safety risks, such as the inability to secure the vehicle when parked.

What repairs are typically needed for the P18B8 code?

Repairs may include replacing damaged wiring, repairing connectors, or replacing the internal mode switch if it is malfunctioning.

How much does it cost to fix the P18B8 code on a GMC Sierra?

Repair costs vary but can range from $150 to $500 depending on the extent of the damage and whether parts like the internal mode switch need replacement.

Is the P18B8 code related to the transmission control module?

While the code primarily concerns the internal mode switch, issues with the transmission control module or its communication may also contribute.

Can a low battery or electrical issue cause the P18B8 code?

Yes, electrical issues like low voltage or a weak battery can potentially cause communication errors, leading to the P18B8 code.

Discuss the causes and fixes for P18B8 2017 GMC Sierra OBDII Code

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