AutoCodes – GMC – P18BC 2014 GMC Sierra

P18BC 2014 GMC Sierra Code - Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range

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: P18BC 2014 GMC Sierra indicates Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range.
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 189

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 P18BC 2014 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 C signal circuit has an invalid voltage range of 1.68 – 2.38 V, for 2.7 s.

OBDII Code P18BC 2014 GMC Sierra - Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range - AutoCodes.com — P18BC 2014 GMC Sierra Code - Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18BC 2014 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 P18BC 2014 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 P18BC 2014 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 P18BC 2014 GMC Sierra code?

Need more information on how to fix the P18BC 2014 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 P18BC 2014 GMC Sierra Code

1. What are the common symptoms of OBDII code P18BC in a 2014 GMC Sierra?

The common symptoms of OBDII code P18BC, Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range in a 2014 GMC Sierra, may include issues with shifting gears, the transmission not responding correctly, and the Check Engine light illuminating on the dashboard.

2. What could cause the OBDII code P18BC in a 2014 GMC Sierra?

The OBDII code P18BC in a 2014 GMC Sierra is typically caused by a malfunction in the internal mode switch 'C' circuit, which may result from wiring issues, a faulty internal mode switch, or a problem with the transmission control module.

3. How can I diagnose the OBDII code P18BC in my 2014 GMC Sierra?

Diagnosing the OBDII code P18BC in a 2014 GMC Sierra involves using a diagnostic scanner to retrieve the trouble codes, checking the internal mode switch 'C' circuit for continuity and proper voltage, inspecting the wiring for any damage, and testing the internal mode switch for functionality.

4. Is it safe to continue driving with the OBDII code P18BC in my 2014 GMC Sierra?

It is not recommended to continue driving with the OBDII code P18BC in a 2014 GMC Sierra, as it can lead to transmission issues and potential safety hazards. It is best to address the problem promptly to prevent further damage.

5. Can I repair the OBDII code P18BC in my 2014 GMC Sierra myself?

Repairing the OBDII code P18BC in a 2014 GMC Sierra may require advanced automotive knowledge and tools. While simple fixes like checking the wiring connections can be done by DIY enthusiasts, diagnosing and repairing internal components may be best left to professional mechanics.

6. How much does it typically cost to repair the OBDII code P18BC in a 2014 GMC Sierra?

The cost to repair the OBDII code P18BC in a 2014 GMC Sierra can vary depending on the underlying cause of the issue. It may range from a few hundred dollars for basic repairs like fixing wiring connections to over a thousand dollars if internal components need replacement.

7. Can a faulty internal mode switch cause the OBDII code P18BC in a 2014 GMC Sierra?

Yes, a faulty internal mode switch can cause the OBDII code P18BC in a 2014 GMC Sierra. If the switch fails to function correctly or gets stuck in the off position, it can trigger the code and lead to transmission-related problems.

8. Are there any preventive measures to avoid the OBDII code P18BC in a 2014 GMC Sierra?

To prevent the OBDII code P18BC in a 2014 GMC Sierra, it's essential to maintain regular vehicle inspections, address any transmission-related issues promptly, and follow the manufacturer's recommended maintenance schedule to ensure the internal components function correctly.

9. How urgent is it to address the OBDII code P18BC in a 2014 GMC Sierra?

Addressing the OBDII code P18BC in a 2014 GMC Sierra is important to prevent potential transmission damage and ensure the vehicle operates safely. It is recommended to address the issue as soon as possible to avoid costly repairs and safety risks.

10. Can resetting the Check Engine light resolve the OBDII code P18BC in a 2014 GMC Sierra?

Simply resetting the Check Engine light will not resolve the OBDII code P18BC in a 2014 GMC Sierra, as the underlying issue causing the fault code will still need to be diagnosed and repaired. Resetting the light without addressing the problem may lead to recurring issues.