AutoCodes – Chevrolet – P18C1 2017 Chevrolet Silverado

P18C1 2017 Chevrolet Silverado Code - Internal Mode Switch 'C' 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: P18C1 2017 Chevrolet Silverado indicates Internal Mode Switch 'C' 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.

Save to My Repairs My Repairs

AI answers can be wrong. Verify repairs with testing. Open full chat

Code Popularity 257

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
Add Comment

💬 Need more help? Ask Coddy for instant answers — it's free!

Code P18C1 2017 Chevrolet Silverado 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 0.70 – 0.96 V, for 2.7 s.

OBDII Code P18C1 2017 Chevrolet Silverado - Internal Mode Switch 'C' Circuit Stuck On Invalid Voltage Range - AutoCodes.com — P18C1 2017 Chevrolet Silverado Code - Internal Mode Switch 'C' Circuit Stuck On Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18C1 2017 Chevrolet Silverado?

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 P18C1 2017 Chevrolet Silverado?

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 P18C1 2017 Chevrolet Silverado 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 P18C1 2017 Chevrolet Silverado code?

Need more information on how to fix the P18C1 2017 Chevrolet Silverado code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P18C1 2017 Chevrolet Silverado code diagnosed by a professional: Find a repair shop in your area

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 P18C1 2017 Chevrolet Silverado Code

What does the OBDII code P18C1 mean for a 2017 Chevrolet Silverado?

Code P18C1 indicates that the Internal Mode Switch 'C' Circuit is stuck on an invalid voltage range, which affects the transmission's ability to identify the correct gear position.

What are the common symptoms of code P18C1 in a 2017 Chevrolet Silverado?

Symptoms may include erratic shifting, transmission stuck in one gear, reduced power, or the transmission not engaging properly.

What causes code P18C1 to appear in a 2017 Chevrolet Silverado?

Common causes include wiring issues, a faulty internal mode switch, damaged connectors, or problems within the transmission control module (TCM).

How can I diagnose code P18C1 in my 2017 Chevrolet Silverado?

Start by inspecting the wiring and connectors related to the internal mode switch for damage or corrosion. Use a scan tool to monitor voltage readings and verify the switch's operation.

Can driving with code P18C1 cause damage to my 2017 Chevrolet Silverado?

Yes, driving with this code can lead to transmission wear or failure due to improper gear operation. Address the issue promptly to avoid further damage.

How do I fix code P18C1 in a 2017 Chevrolet Silverado?

Repairs may involve replacing the internal mode switch, repairing damaged wiring, cleaning corroded connectors, or reprogramming the TCM if necessary.

Is code P18C1 related to the transmission in a 2017 Chevrolet Silverado?

Yes, it directly affects the transmission's ability to determine the correct gear position, impacting overall performance.

Will clearing the code P18C1 fix the problem in a 2017 Chevrolet Silverado?

Clearing the code may temporarily reset the system, but the underlying issue needs to be repaired to prevent the code from returning.

How much does it cost to fix code P18C1 on a 2017 Chevrolet Silverado?

Repair costs vary depending on the cause, ranging from $100 for simple wiring repairs to over $1,000 if the internal mode switch or TCM needs replacement.

Can code P18C1 be prevented in a 2017 Chevrolet Silverado?

Regular maintenance, such as inspecting wiring, cleaning connectors, and avoiding water intrusion in the transmission system, can help prevent this code from occurring.