AutoCodes – GMC – P18B5 2017 GMC Sierra

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

Quick Answer

The internal mode switch indicates the Transmission Control Module (TCM) which gear position the vehicle operator has selected. Common causes include Faulty Transmission Internal Mode Switch, Transmission Internal Mode Switch harness is open or shorted, Transmission Internal Mode Switch circuit poor electrical connection. 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 Faulty Transmission Internal Mode Switch, Transmission Internal Mode Switch harness is open or shorted, Transmission Internal Mode Switch circuit poor electrical connection.
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.

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Code Popularity 168

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 23, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P18B5 2017 GMC Sierra Description

The internal mode switch indicates the Transmission Control Module (TCM) which gear position the vehicle operator has selected. The internal mode switch consists of 5 separate hall effect switches. Each hall effect switch is supplied with a 9 V reference circuit and a signal circuit from the TCM. Each signal circuit for each gear selector position will have either a voltage reading of 0.70–0.96 V indicating On or 1.68–2.38 V indicating Off. The voltage values on each internal mode switch circuit will change and are dependent on the position of the gear selector. The state of each internal mode switch A/B/C/P/S signal circuit is displayed on the scan tool. The Diagnostic Trouble Code (DTC) will be set when the TCM has detected the internal mode switch A signal circuit voltage is between 0.966–1.68 V, for 1.75 s.

OBDII Code P18B5 2017 GMC Sierra - Internal Mode Switch 'A' Circuit Shorted - AutoCodes.com — P18B5 2017 GMC Sierra Code - Internal Mode Switch 'A' Circuit Shorted

What does this mean?

What are the Possible Causes of the DTC P18B5 2017 GMC Sierra?

Faulty Transmission Internal Mode Switch
Transmission Internal Mode Switch harness is open or shorted
Transmission Internal Mode Switch circuit poor electrical connection
Faulty Transmission Control Module (TCM)

How to Fix the DTC P18B5 2017 GMC Sierra?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P18B5 2017 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P18B5 2017 GMC Sierra code?

Need more information on how to fix the P18B5 2017 GMC Sierra code? Get Access to Factory Service Manuals

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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.