AutoCodes – GMC – P18C2 2014 GMC Sierra

P18C2 2014 GMC Sierra Code - Internal Mode Switch 'P' 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: P18C2 2014 GMC Sierra indicates Internal Mode Switch 'P' 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 169

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 P18C2 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 P signal circuit has an invalid voltage range of 0.70 – 0.96 V for 2.7 s.

OBDII Code P18C2 2014 GMC Sierra - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range - AutoCodes.com — P18C2 2014 GMC Sierra Code - Internal Mode Switch 'P' Circuit Stuck On Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18C2 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 P18C2 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 P18C2 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 P18C2 2014 GMC Sierra code?

Need more information on how to fix the P18C2 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 P18C2 2014 GMC Sierra Code

1. What are the common symptoms of OBDII code P18C2 in a 2014 GMC Sierra?

- Common symptoms include issues with shifting gears, the vehicle staying in one gear, erratic shifting patterns, and the Check Engine Light illuminating.

2. What does the OBDII code P18C2 'Internal Mode Switch P Circuit Stuck On Invalid Voltage Range' mean for a 2014 GMC Sierra?

- This code indicates that there is an electrical issue with the internal mode switch circuit, specifically related to an invalid voltage range being detected.

3. What are the possible causes of OBDII code P18C2 in a 2014 GMC Sierra?

- Potential causes include a faulty internal mode switch, damaged wiring or connectors in the circuit, a malfunctioning transmission control module, or low voltage in the system.

4. How serious is the OBDII code P18C2 in a 2014 GMC Sierra?

- This code can lead to drivability issues and potentially cause further damage to the transmission if left unresolved. It is advisable to address the issue promptly.

5. Can I continue driving my 2014 GMC Sierra with OBDII code P18C2?

- It is not recommended to continue driving the vehicle with this code present, as it can impact the transmission's performance and reliability.

6. How can I diagnose and repair OBDII code P18C2 in my 2014 GMC Sierra?

- Diagnosis typically involves checking the internal mode switch, inspecting the wiring and connectors for damage, testing the transmission control module, and verifying voltage levels in the circuit.

7. Is it possible to reset the OBDII code P18C2 in a 2014 GMC Sierra?

- Resetting the code may temporarily turn off the Check Engine Light, but if the underlying issue is not addressed, the code is likely to return.

8. Are there any DIY repair tips for addressing OBDII code P18C2 in a 2014 GMC Sierra?

- DIY repairs for this code may involve checking and cleaning the connectors, ensuring proper wiring connections, and testing voltage levels if you have the necessary tools and expertise.

9. How much does it cost to fix OBDII code P18C2 in a 2014 GMC Sierra?

- The cost of repairs can vary depending on the exact cause of the issue, parts needed, and labor rates. It is recommended to consult a professional mechanic for an accurate estimate.

10. Can OBDII code P18C2 in a 2014 GMC Sierra cause other problems if not fixed promptly?

- If left unresolved, this code can potentially cause further damage to the transmission and lead to more severe drivability issues in the vehicle. It is best to address the issue promptly.