AutoCodes – Chevrolet – P18BC 2015 Chevrolet Silverado

P18BC 2015 Chevrolet Silverado 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 2015 Chevrolet Silverado 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 513

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 2015 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 1.68 – 2.38 V, for 2.7 s.

OBDII Code P18BC 2015 Chevrolet Silverado - Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range - AutoCodes.com — P18BC 2015 Chevrolet Silverado Code - Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18BC 2015 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 P18BC 2015 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 P18BC 2015 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 P18BC 2015 Chevrolet Silverado code?

Need more information on how to fix the P18BC 2015 Chevrolet Silverado 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 P18BC 2015 Chevrolet Silverado Code

1. What does the OBDII code P18BC mean on a 2015 Chevrolet Silverado?

P18BC indicates that the Internal Mode Switch 'C' circuit is stuck off due to an invalid voltage range detected by the transmission control module (TCM).

2. What are the common symptoms of the P18BC code?

Symptoms may include transmission shifting issues, failure to engage specific gears, the check engine light turning on, and erratic transmission behavior.

3. What causes the P18BC code to appear?

Common causes include a faulty internal mode switch, damaged wiring or connectors in the circuit, or a malfunctioning transmission control module.

4. Can I drive my 2015 Silverado with the P18BC code active?

Driving with this code may lead to further transmission issues or unsafe driving conditions. It's best to address the issue promptly.

5. How is the P18BC code diagnosed?

A mechanic will use a scan tool to verify the code, inspect the wiring and connectors for damage, test the internal mode switch, and check the transmission control module for faults.

6. How do I fix a P18BC code on my Silverado?

Repairs may include replacing the internal mode switch, repairing or replacing damaged wiring or connectors, or reprogramming or replacing the transmission control module.

7. What is an internal mode switch in a Silverado's transmission?

The internal mode switch communicates the gear selector position to the transmission control module to ensure proper gear engagement.

8. How much does it cost to repair the P18BC code?

Repair costs vary but may range from $200 to $600, depending on whether the issue is a simple wiring repair or a replacement of the internal mode switch.

9. Can a low battery cause the P18BC code?

While uncommon, a weak or failing battery can sometimes cause voltage-related issues that lead to this code. Ensure the battery and charging system are in good condition.

10. Does the P18BC code require reprogramming the TCM?

In some cases, reprogramming or updating the TCM software may resolve the issue, particularly if no physical faults are found in the circuit.