AutoCodes – Chevrolet – P18B6 2015 Chevrolet Silverado

P18B6 2015 Chevrolet Silverado 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 2015 Chevrolet Silverado 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 233

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

OBDII Code P18B6 2015 Chevrolet Silverado - Internal Mode Switch 'B' Circuit Shorted - AutoCodes.com — P18B6 2015 Chevrolet Silverado Code - Internal Mode Switch 'B' Circuit Shorted

What does this mean?

What are the Possible Causes of the DTC P18B6 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 P18B6 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 P18B6 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 P18B6 2015 Chevrolet Silverado code?

Need more information on how to fix the P18B6 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 P18B6 2015 Chevrolet Silverado Code

1. What does the OBDII code P18B6 mean on a 2015 Chevrolet Silverado?

P18B6 indicates an issue with the Internal Mode Switch (IMS) 'B' circuit, specifically a shorted condition that disrupts proper transmission operation.

2. What are the common symptoms of code P18B6 in a 2015 Chevrolet Silverado?

Symptoms may include the transmission being stuck in one gear, erratic shifting, the Check Engine Light being illuminated, and reduced overall drivability.

3. What causes the P18B6 code to appear on a 2015 Chevrolet Silverado?

The code is typically caused by a short circuit or damage in the wiring or connectors to the Internal Mode Switch, a faulty switch assembly, or issues within the transmission control module (TCM).

4. Can I drive my 2015 Chevrolet Silverado with a P18B6 code?

While the truck may still drive, it is not recommended, as the transmission could operate improperly, leading to further damage or unsafe driving conditions.

5. How is the P18B6 code diagnosed in a 2015 Chevrolet Silverado?

A technician will inspect the IMS wiring and connectors for damage, test the switch for proper operation, and use a scan tool to monitor transmission data and confirm the fault.

6. What repairs are needed to fix the P18B6 code on a 2015 Chevrolet Silverado?

Repairs may involve replacing or repairing damaged wiring, connectors, or the Internal Mode Switch, and in rare cases, reprogramming or replacing the transmission control module.

7. How much does it cost to repair a P18B6 code on a 2015 Chevrolet Silverado?

Repair costs can range from $150 to $600 depending on whether the issue lies with the wiring, the IMS itself, or the TCM.

8. Can a faulty battery cause the P18B6 code on a 2015 Chevrolet Silverado?

While unlikely, a weak or failing battery can sometimes exacerbate electrical issues, leading to false codes or poor communication within the transmission system.

9. Is the Internal Mode Switch 'B' part of the transmission?

Yes, the Internal Mode Switch (IMS) is integrated into the transmission and monitors gear positions to ensure proper operation.

10. Can clearing the P18B6 code fix the issue on a 2015 Chevrolet Silverado?

Clearing the code without addressing the root cause may result in the code returning. Proper diagnosis and repair of the underlying problem are necessary.