AutoCodes – Chevrolet – P18B8 Chevrolet

P18B8 Chevrolet Code - Internal Mode Switch 'P' 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: P18B8 Chevrolet indicates Internal Mode Switch 'P' 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 1,599

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 P18B8 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 P signal circuit voltage is between 0.966–1.68 V, for 1.75 s.

OBDII Code P18B8 Chevrolet - Internal Mode Switch 'P' Circuit Shorted - AutoCodes.com — P18B8 Chevrolet Code - Internal Mode Switch 'P' Circuit Shorted

What does this mean?

What are the Possible Causes of the DTC P18B8 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 P18B8 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 P18B8 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 P18B8 Chevrolet code?

Need more information on how to fix the P18B8 Chevrolet code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P18B8 Chevrolet code diagnosed by a professional: Find a repair shop in your area

Information for Specific Chevrolet Models

P18B8 2014 Chevrolet Silverado — Internal Mode Switch 'P' Circuit Shorted
P18B8 2015 Chevrolet Silverado — Internal Mode Switch 'P' Circuit Shorted
P18B8 2016 Chevrolet Silverado — Internal Mode Switch 'P' Circuit Shorted
P18B8 2017 Chevrolet Silverado — Internal Mode Switch 'P' Circuit Shorted
P18B8 2018 Chevrolet Silverado — Internal Mode Switch 'P' 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 P18B8 Chevrolet Code

1. What are common symptoms of OBDII code P18B8 in a Chevrolet related to the Internal Mode Switch 'P' Circuit Shorted?

- Common symptoms include difficulty shifting gears, transmission issues, and illumination of the check engine light.

2. What can cause the Internal Mode Switch 'P' Circuit Shorted OBDII code P18B8 in a Chevrolet?

- The code can be triggered by a short circuit in the internal mode switch, damaged wiring, or a faulty internal mode switch itself.

3. How serious is the OBDII code P18B8 related to the Internal Mode Switch 'P' Circuit Shorted in a Chevrolet?

- This code can affect the proper operation of the transmission, so it is important to address it promptly to prevent further damage.

4. Can I continue driving my Chevrolet with the OBDII code P18B8 present?

- It is not recommended to continue driving with this code active, as it can lead to transmission issues and potential safety hazards.

5. How can I diagnose the Internal Mode Switch 'P' Circuit Shorted OBDII code P18B8 in my Chevrolet?

- Diagnosis typically involves using a scan tool to read the code, checking the internal mode switch and related wiring for shorts, and performing a thorough inspection.

6. What are some repair tips for fixing the Internal Mode Switch 'P' Circuit Shorted OBDII code P18B8 in a Chevrolet?

- Repair tips may include repairing or replacing damaged wiring, replacing the internal mode switch if necessary, and clearing the code from the vehicle's computer.

7. Is it possible to reset the OBDII code P18B8 in a Chevrolet without fixing the underlying issue?

- While you can clear the code using a scan tool, it is important to address the root cause of the issue to prevent it from reoccurring.

8. How much does it typically cost to repair the Internal Mode Switch 'P' Circuit Shorted OBDII code P18B8 in a Chevrolet?

- The cost of repair can vary depending on the extent of the damage and whether professional assistance is needed, but it is generally recommended to consult a mechanic for an accurate estimate.

9. Can a DIY enthusiast fix the OBDII code P18B8 related to the Internal Mode Switch 'P' Circuit Shorted in a Chevrolet?

- While knowledgeable DIY enthusiasts may be able to address this issue, it is recommended to have a professional mechanic diagnose and repair the problem to ensure it is fixed correctly.

10. How can I prevent the Internal Mode Switch 'P' Circuit Shorted OBDII code P18B8 from occurring in my Chevrolet in the future?

- Regular maintenance checks, avoiding harsh driving conditions, and promptly addressing any transmission issues can help prevent this code from reoccurring.