AutoCodes – Chevrolet – P18B6 Chevrolet

P18B6 Chevrolet Code - Internal Mode Switch 'B' Circuit Shorted

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: P18B6 Chevrolet indicates Internal Mode Switch 'B' Circuit Shorted.
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 1,573

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 P18B6 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 B signal circuit voltage is between 0.966–1.68 V, for 1.75 s.

OBDII Code P18B6 Chevrolet - Internal Mode Switch 'B' Circuit Shorted - AutoCodes.com — P18B6 Chevrolet Code - Internal Mode Switch 'B' Circuit Shorted

What does this mean?

What are the Possible Causes of the DTC P18B6 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 P18B6 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 P18B6 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.

Need more information about the P18B6 Chevrolet code?

Need more information on how to fix the P18B6 Chevrolet code? Get Access to Factory Service Manuals

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Information for Specific Chevrolet Models

P18B6 2014 Chevrolet Silverado — Internal Mode Switch 'B' Circuit Shorted
P18B6 2015 Chevrolet Silverado — Internal Mode Switch 'B' Circuit Shorted
P18B6 2016 Chevrolet Silverado — Internal Mode Switch 'B' Circuit Shorted
P18B6 2017 Chevrolet Silverado — Internal Mode Switch 'B' Circuit Shorted
P18B6 2018 Chevrolet Silverado — Internal Mode Switch 'B' Circuit Shorted

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 P18B6 Chevrolet Code

1. What are common symptoms of OBDII code P18B6 (Internal Mode Switch 'B' Circuit Shorted) in a Chevrolet?

- Common symptoms include issues with gear shifting, harsh shifting, transmission problems, and an illuminated check engine light.

2. What could cause the Internal Mode Switch 'B' Circuit Shorted code to trigger in a Chevrolet?

- Possible causes include a faulty internal mode switch, damaged wiring or connectors in the circuit, or a problem with the transmission control module.

3. How serious is the P18B6 code in a Chevrolet vehicle?

- The code should be addressed promptly as it can lead to transmission issues and affect the vehicle's drivability.

4. Can driving with the P18B6 code cause further damage to the vehicle?

- Continued driving with this code can potentially cause damage to the transmission system, so it's recommended to address the issue as soon as possible.

5. How can I diagnose and repair the Internal Mode Switch 'B' Circuit Shorted code in my Chevrolet?

- Diagnosis typically involves inspecting the internal mode switch, checking the circuit for shorts, and testing the transmission control module. Repairs may involve replacing the internal mode switch or repairing damaged wiring.

6. Is it safe to continue driving my Chevrolet with the P18B6 code present?

- It is not recommended to drive the vehicle with this code present, as it can lead to transmission issues and potentially cause further damage.

7. Can I reset the check engine light after fixing the P18B6 code in my Chevrolet?

- Yes, once the underlying issue causing the code is fixed, the check engine light can be reset using an OBDII scanner.

8. How much does it typically cost to repair the Internal Mode Switch 'B' Circuit Shorted code in a Chevrolet?

- The cost of repair can vary depending on the exact cause of the issue, but it may involve parts replacement and labor costs, which can range from a few hundred to over a thousand dollars.

9. Is the P18B6 code specific to Chevrolet vehicles only?

- While the code P18B6 specifically references Chevrolet vehicles, similar issues with the internal mode switch circuit can occur in other makes and models as well.

10. How can I prevent the Internal Mode Switch 'B' Circuit Shorted code from recurring in my Chevrolet?

- Regular maintenance and timely repairs of transmission-related components can help prevent the recurrence of the P18B6 trouble code in your Chevrolet.