AutoCodes – Chevrolet – P18C3 Chevrolet

P18C3 Chevrolet Code - Internal Mode Switch 'S' 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: P18C3 Chevrolet indicates Internal Mode Switch 'S' 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 1,162

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 P18C3 Chevrolet 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 has an internal mode switch S signal circuit has an invalid voltage range of 0.70 – 0.96 V, for 2.7 s.

OBDII Code P18C3 Chevrolet - Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range - AutoCodes.com — P18C3 Chevrolet Code - Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18C3 Chevrolet?

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 P18C3 Chevrolet?

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 P18C3 Chevrolet 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 P18C3 Chevrolet code?

Need more information on how to fix the P18C3 Chevrolet code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P18C3 Chevrolet code diagnosed by a professional: Find a repair shop in your area

Information for Specific Chevrolet Models

P18C3 2014 Chevrolet Silverado — Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range
P18C3 2015 Chevrolet Silverado — Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range
P18C3 2016 Chevrolet Silverado — Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range
P18C3 2017 Chevrolet Silverado — Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range
P18C3 2018 Chevrolet Silverado — Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range

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 P18C3 Chevrolet Code

1. What are the common symptoms of OBDII code P18C3 in a Chevrolet vehicle?

The common symptoms of OBDII code P18C3 include issues with shifting gears, the inability to start the vehicle, and the Check Engine Light being illuminated on the dashboard.

2. What causes the Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range error in a Chevrolet?

The P18C3 code in a Chevrolet is typically caused by a faulty internal mode switch, damaged wiring or connectors, or a malfunctioning transmission control module.

3. How serious is the P18C3 OBDII code in a Chevrolet vehicle?

The P18C3 code can lead to drivability issues and potential safety concerns due to incorrect gear shifting. It is recommended to address this issue promptly to avoid further damage to the transmission.

4. Can I continue driving my Chevrolet with the P18C3 code present?

It is not recommended to continue driving your Chevrolet with the P18C3 code present, as it can lead to transmission problems and potential safety hazards. It is best to have the issue diagnosed and repaired as soon as possible.

5. How can I diagnose the Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range issue in my Chevrolet?

Diagnosing the P18C3 code usually involves using a diagnostic scanner to retrieve the fault codes, inspecting the internal mode switch and its circuit, checking for damaged wiring or connectors, and testing the transmission control module.

6. What are some repair tips for fixing the P18C3 code in a Chevrolet?

Repairing the P18C3 code may involve replacing the internal mode switch, repairing or replacing damaged wiring or connectors, or reprogramming the transmission control module. It is recommended to consult a professional mechanic for accurate diagnosis and repair.

7. Can a DIY enthusiast fix the P18C3 code issue in a Chevrolet?

While some basic troubleshooting steps can be performed by a DIY enthusiast, diagnosing and repairing the P18C3 code may require specialized tools and expertise. It is advisable to seek help from a qualified mechanic for proper diagnosis and repair.

8. How much does it cost to repair the Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range problem in a Chevrolet?

The cost of repairing the P18C3 code in a Chevrolet can vary depending on the extent of the issue, the parts needed for replacement, and the labor charges. It is best to get a few quotes from different repair shops to compare prices.

9. Is the P18C3 OBDII code covered under Chevrolet's warranty?

The coverage of the P18C3 OBDII code under Chevrolet's warranty depends on the vehicle's age, mileage, and warranty status. It is recommended to check with a Chevrolet dealership or refer to the vehicle's warranty information for specific details.

10. How can I prevent the Internal Mode Switch 'S' Circuit Stuck On Invalid Voltage Range issue from reoccurring in my Chevrolet?

To prevent the recurrence of the P18C3 code, it is essential to ensure regular maintenance of the transmission system, timely inspections, and prompt repairs of any related issues. Following the manufacturer's recommended maintenance schedule can also help prevent future problems.