AutoCodes – GMC – P18B7 2017 GMC Sierra

P18B7 2017 GMC Sierra Code - Internal Mode Switch 'C' 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: P18B7 2017 GMC Sierra indicates Internal Mode Switch 'C' 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 321

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 P18B7 2017 GMC Sierra 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 voltage is between 0.966–1.68 V, for 1.75 s.

OBDII Code P18B7 2017 GMC Sierra - Internal Mode Switch 'C' Circuit Shorted - AutoCodes.com — P18B7 2017 GMC Sierra Code - Internal Mode Switch 'C' Circuit Shorted

What does this mean?

What are the Possible Causes of the DTC P18B7 2017 GMC Sierra?

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 P18B7 2017 GMC Sierra?

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 P18B7 2017 GMC Sierra 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 P18B7 2017 GMC Sierra code?

Need more information on how to fix the P18B7 2017 GMC Sierra 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 P18B7 2017 GMC Sierra Code

1. What are the common symptoms of OBDII code P18B7 on a 2017 GMC Sierra?

- Common symptoms include issues with gear shifting, erratic transmission behavior, and the vehicle going into limp mode.

2. What does the OBDII code P18B7 'Internal Mode Switch C Circuit Shorted' mean for a 2017 GMC Sierra?

- This code indicates a malfunction in the internal mode switch circuit C, which can affect the transmission's operation.

3. What are the possible causes of OBDII code P18B7 on a 2017 GMC Sierra?

- Possible causes include a short circuit in the internal mode switch 'C' circuit, a faulty internal mode switch, or damaged wiring in the circuit.

4. How can I diagnose the OBDII code P18B7 on my 2017 GMC Sierra?

- Diagnosing this code typically involves using a scan tool to check for the specific fault code, inspecting the internal mode switch and its wiring, and performing continuity tests.

5. Can I continue driving my 2017 GMC Sierra with OBDII code P18B7?

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

6. How can I repair OBDII code P18B7 on my 2017 GMC Sierra?

- Repairing this code may involve replacing the internal mode switch, repairing any damaged wiring, or addressing the short circuit in the circuit.

7. Is it possible to reset the OBDII code P18B7 on a 2017 GMC Sierra without fixing the underlying issue?

- Resetting the code without fixing the underlying problem will likely result in the code reappearing once the vehicle is driven again.

8. Are there any DIY tips for troubleshooting OBDII code P18B7 on a 2017 GMC Sierra?

- DIY tips may include checking the internal mode switch connections, inspecting the wiring for damage, and ensuring proper grounding in the circuit.

9. How long does it typically take to repair OBDII code P18B7 on a 2017 GMC Sierra?

- The repair time can vary depending on the exact cause of the issue, but it may take a few hours to a full day to diagnose and fix the problem.

10. Can a professional mechanic help with resolving OBDII code P18B7 on a 2017 GMC Sierra?

- Yes, a professional mechanic with experience in diagnosing and repairing transmission-related issues can assist in resolving the code P18B7 on your GMC Sierra.