AutoCodes – GMC – P18C0 2015 GMC Sierra

P18C0 2015 GMC Sierra Code - Internal Mode Switch 'B' Circuit Stuck On 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: P18C0 2015 GMC Sierra indicates Internal Mode Switch 'B' Circuit Stuck On 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 158

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 P18C0 2015 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 B signal circuit has an invalid voltage range of 0.70 – 0.96 V for 2.7 s.

OBDII Code P18C0 2015 GMC Sierra - Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range - AutoCodes.com — P18C0 2015 GMC Sierra Code - Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18C0 2015 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 P18C0 2015 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 P18C0 2015 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 P18C0 2015 GMC Sierra code?

Need more information on how to fix the P18C0 2015 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 P18C0 2015 GMC Sierra Code

1. What are the common symptoms of OBDII code P18C0 in a 2015 GMC Sierra?

The common symptoms of OBDII code P18C0 in a 2015 GMC Sierra include issues with shifting gears, the transmission being stuck in a single gear, and the vehicle not starting.

2. What does the OBDII code P18C0 'Internal Mode Switch 'B' Circuit Stuck On Invalid Voltage Range' mean for a 2015 GMC Sierra?

This code indicates a problem with the internal mode switch 'B' circuit in the transmission, specifically that it is stuck in an invalid voltage range.

3. What are the possible causes of OBDII code P18C0 in a 2015 GMC Sierra?

Possible causes of OBDII code P18C0 in a 2015 GMC Sierra include a faulty internal mode switch, damaged wiring or connectors in the circuit, or a problem with the transmission control module.

4. How can I diagnose the OBDII code P18C0 in my 2015 GMC Sierra?

Diagnosing OBDII code P18C0 in a 2015 GMC Sierra involves using a scan tool to retrieve the code, checking the internal mode switch and its circuit for any visible damage, and testing the voltage readings in the circuit.

5. Is it safe to continue driving my 2015 GMC Sierra with OBDII code P18C0 present?

It is not recommended to continue driving your 2015 GMC Sierra with OBDII code P18C0 present, as it can lead to further damage to the transmission and other related components.

6. Can I repair OBDII code P18C0 in my 2015 GMC Sierra myself?

While some DIY enthusiasts may attempt to repair OBDII code P18C0 in a 2015 GMC Sierra, it is recommended to seek professional help due to the complexity of transmission-related issues.

7. How much does it cost to fix OBDII code P18C0 in a 2015 GMC Sierra?

The cost of fixing OBDII code P18C0 in a 2015 GMC Sierra can vary depending on the exact cause of the issue, but it may range from a few hundred to over a thousand dollars for parts and labor.

8. Can a damaged internal mode switch cause OBDII code P18C0 in a 2015 GMC Sierra?

Yes, a damaged internal mode switch can cause OBDII code P18C0 in a 2015 GMC Sierra as it may result in the circuit being stuck in an invalid voltage range.

9. How urgent is it to address OBDII code P18C0 in a 2015 GMC Sierra?

It is recommended to address OBDII code P18C0 in a 2015 GMC Sierra as soon as possible to prevent further damage to the transmission and ensure the vehicle operates safely.

10. What is the typical repair process for resolving OBDII code P18C0 in a 2015 GMC Sierra?

The typical repair process for resolving OBDII code P18C0 in a 2015 GMC Sierra involves diagnosing the exact cause, replacing any faulty components such as the internal mode switch or repairing damaged wiring, and clearing the code from the system.