AutoCodes – Chevrolet – P18C1 2018 Chevrolet Silverado

P18C1 2018 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 2018 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 279

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 2018 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 2018 Chevrolet Silverado - Internal Mode Switch 'C' Circuit Stuck On Invalid Voltage Range - AutoCodes.com — P18C1 2018 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 2018 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 2018 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 2018 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 2018 Chevrolet Silverado code?

Need more information on how to fix the P18C1 2018 Chevrolet Silverado code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P18C1 2018 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 2018 Chevrolet Silverado Code

1. What are the common symptoms of OBDII code P18C1 in a 2018 Chevrolet Silverado?

The common symptoms of OBDII code P18C1 in a 2018 Chevrolet Silverado include issues with shifting gears, the transmission not engaging properly, and the vehicle going into limp mode.

2. What does the OBDII code P18C1 'Internal Mode Switch 'C' Circuit Stuck On Invalid Voltage Range' indicate in a 2018 Chevrolet Silverado?

The code P18C1 indicates a fault with the internal mode switch 'C' circuit in the transmission, specifically that it is stuck in an invalid voltage range.

3. What are the possible causes of OBDII code P18C1 in a 2018 Chevrolet Silverado?

Possible causes of OBDII code P18C1 in a 2018 Chevrolet Silverado include a faulty internal mode switch, wiring issues, a defective transmission control module, or a poor electrical connection.

4. How serious is the OBDII code P18C1 issue in a 2018 Chevrolet Silverado?

The OBDII code P18C1 can lead to transmission shifting issues and potentially cause the vehicle to go into a limp mode, impacting the drivability of the vehicle. It is best to address this issue promptly to prevent further damage.

5. Can I continue driving my 2018 Chevrolet Silverado with OBDII code P18C1?

It is not recommended to continue driving your 2018 Chevrolet Silverado with the OBDII code P18C1 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.

6. How can I diagnose OBDII code P18C1 in my 2018 Chevrolet Silverado?

Diagnosing OBDII code P18C1 in a 2018 Chevrolet Silverado typically involves checking the internal mode switch, inspecting the wiring and connectors, and testing the transmission control module for faults using a diagnostic tool.

7. What are some repair tips for fixing OBDII code P18C1 in a 2018 Chevrolet Silverado?

Repair tips for OBDII code P18C1 may include replacing the internal mode switch, repairing any damaged wiring or connectors, resetting the transmission control module, and ensuring all connections are secure.

8. Can I reset the OBDII code P18C1 in my 2018 Chevrolet Silverado without fixing the underlying issue?

While you can clear the OBDII code P18C1 using a diagnostic tool, it is not recommended to do so without addressing the underlying issue. The problem will likely reoccur if the root cause is not fixed.

9. Is it possible to prevent OBDII code P18C1 from occurring in my 2018 Chevrolet Silverado?

While some factors leading to OBDII code P18C1 may be out of your control, regular maintenance, checking for signs of wear in the transmission system, and addressing any electrical issues promptly can help prevent this code from occurring.

10. How much does it typically cost to repair OBDII code P18C1 in a 2018 Chevrolet Silverado?

The cost to repair OBDII code P18C1 in a 2018 Chevrolet Silverado can vary depending on the exact cause of the issue, parts needed for replacement, and labor costs. It is recommended to consult with a professional mechanic for an accurate estimate.