AutoCodes – Chevrolet – P18BC 2018 Chevrolet Silverado

P18BC 2018 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 2018 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 273

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 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 1.68 – 2.38 V, for 2.7 s.

OBDII Code P18BC 2018 Chevrolet Silverado - Internal Mode Switch 'C' Circuit Stuck Off Invalid Voltage Range - AutoCodes.com — P18BC 2018 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 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 P18BC 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 P18BC 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 P18BC 2018 Chevrolet Silverado code?

Need more information on how to fix the P18BC 2018 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 2018 Chevrolet Silverado Code

1. What does the OBDII code P18BC mean on a 2018 Chevrolet Silverado?

P18BC indicates that the Internal Mode Switch 'C' circuit is stuck off or has an invalid voltage range, which is part of the transmission control system.

2. What are the common symptoms of the P18BC code in a Chevrolet Silverado?

Symptoms may include difficulty shifting gears, the transmission stuck in one gear, the check engine light illuminated, and reduced vehicle performance.

3. What causes the P18BC code to appear in a 2018 Chevrolet Silverado?

Common causes include a faulty internal mode switch, damaged wiring or connectors, poor electrical connections, or issues with the transmission control module (TCM).

4. Can the P18BC code cause drivability problems?

Yes, it can cause gear shifting problems, reduced power, and potentially prevent the vehicle from operating normally.

5. How do you diagnose a P18BC code on a Chevrolet Silverado?

Diagnosis involves scanning the vehicle with an OBDII scanner, checking the internal mode switch and its wiring for damage, and testing the circuit for proper voltage and continuity.

6. Is it safe to drive a 2018 Chevrolet Silverado with a P18BC code?

Driving with this code is not recommended, as it may lead to further transmission damage or unsafe driving conditions.

7. How do you fix the P18BC code in a Chevrolet Silverado?

Repairs typically involve replacing the faulty internal mode switch, repairing or replacing damaged wiring or connectors, or reprogramming/updating the TCM.

8. What tools are needed to repair the P18BC code?

Youâ€™ll need an OBDII scanner, a multimeter for electrical testing, and potentially specialized tools for accessing and replacing the internal mode switch.

9. What is the internal mode switch in a Chevrolet Silverado?

The internal mode switch is a component in the transmission that communicates gear selection and position information to the transmission control module.

10. Can a software update fix the P18BC code on a 2018 Chevrolet Silverado?

In some cases, a software update or reprogramming of the transmission control module may resolve the issue if itâ€™s related to a programming fault.