AutoCodes – Chevrolet – P18BC Chevrolet

P18BC Chevrolet Code - Internal Mode Switch 'C' Circuit Stuck Off 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: P18BC Chevrolet indicates Internal Mode Switch 'C' Circuit Stuck Off 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 1,495

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 P18BC 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 the internal mode switch C signal circuit has an invalid voltage range of 1.68 – 2.38 V, for 2.7 s.

OBDII Code P18BC Chevrolet - Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range - AutoCodes.com — P18BC Chevrolet Code - Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18BC 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 P18BC 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 P18BC 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.

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Information for Specific Chevrolet Models

P18BC 2014 Chevrolet Silverado — Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range
P18BC 2015 Chevrolet Silverado — Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range
P18BC 2016 Chevrolet Silverado — Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range
P18BC 2017 Chevrolet Silverado — Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range
P18BC 2018 Chevrolet Silverado — Internal Mode Switch 'C' Circuit Stuck Off 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 P18BC Chevrolet Code

1. What are the common symptoms of OBDII code P18BC (Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range)?

- Common symptoms include issues with shifting gears, incorrect gear display on the dashboard, and potential limp mode activation.

2. What can cause the OBDII code P18BC to trigger in a Chevrolet vehicle?

- This code is usually triggered by a malfunction in the internal mode switch 'C' circuit, which can be caused by wiring issues, a faulty internal mode switch, or an issue with the transmission control module.

3. How serious is the OBDII code P18BC in a Chevrolet vehicle?

- While the vehicle may still be driveable with this code present, it is important to address it promptly to avoid potential transmission issues and further damage.

4. Can I continue driving my Chevrolet with the P18BC code present?

- It is not recommended to drive the vehicle with this code present for an extended period, as it can lead to potential transmission problems and impact the overall drivability of the vehicle.

5. How can I diagnose the OBDII code P18BC in my Chevrolet?

- Diagnosing this code typically involves using a scan tool to read the code, checking the internal mode switch 'C' circuit for faults, and inspecting the wiring and connections for any issues.

6. What are some repair tips for fixing the OBDII code P18BC in a Chevrolet?

- Repair tips may include checking and repairing any damaged wiring, replacing the internal mode switch if necessary, and resetting the code to see if it reoccurs.

7. Can a DIY enthusiast fix the OBDII code P18BC issue in a Chevrolet?

- While some basic troubleshooting and repairs can be done by a DIY enthusiast, complex issues with the internal mode switch or transmission control module may require professional diagnosis and repair.

8. How much does it typically cost to repair the OBDII code P18BC in a Chevrolet?

- The cost of repair can vary depending on the underlying issue, but it may involve expenses for parts replacement, labor costs, and diagnostic fees.

9. How long does it take to fix the OBDII code P18BC in a Chevrolet?

- The repair time can vary based on the complexity of the issue and the availability of parts, but it is advisable to consult with a mechanic for a more accurate time estimate.

10. Can resetting the OBDII code P18BC on my Chevrolet resolve the issue permanently?

- Resetting the code may temporarily clear the warning light, but if the underlying issue is not fixed, the code is likely to reappear. It is important to diagnose and address the root cause of the problem for a permanent solution.