AutoCodes – GMC – P18B5 2016 GMC Sierra

P18B5 2016 GMC Sierra Code - Internal Mode Switch 'A' 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: P18B5 2016 GMC Sierra indicates Internal Mode Switch 'A' 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 164

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 P18B5 2016 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 A signal circuit voltage is between 0.966–1.68 V, for 1.75 s.

OBDII Code P18B5 2016 GMC Sierra - Internal Mode Switch 'A' Circuit Shorted - AutoCodes.com — P18B5 2016 GMC Sierra Code - Internal Mode Switch 'A' Circuit Shorted

What does this mean?

What are the Possible Causes of the DTC P18B5 2016 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 P18B5 2016 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 P18B5 2016 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 P18B5 2016 GMC Sierra code?

Need more information on how to fix the P18B5 2016 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 P18B5 2016 GMC Sierra Code

1. What are the common symptoms of OBDII code P18B5 on a 2016 GMC Sierra?

The common symptoms of OBDII code P18B5, which indicates an Internal Mode Switch 'A' Circuit Shorted, may include difficulty shifting gears, erratic shifting behavior, and possibly illumination of the check engine light.

2. What are some possible causes of OBDII code P18B5 on a 2016 GMC Sierra?

Possible causes of OBDII code P18B5 on a 2016 GMC Sierra include a faulty internal mode switch, damaged wiring or connectors related to the switch, or an internal fault within the transmission control module.

3. How can I diagnose OBDII code P18B5 on my 2016 GMC Sierra?

Diagnosing OBDII code P18B5 may involve using a scan tool to retrieve the code, inspecting the internal mode switch and its wiring for damage, and testing the switch for proper functionality. It is recommended to consult a professional mechanic for accurate diagnosis.

4. Can I continue to drive my 2016 GMC Sierra with OBDII code P18B5 present?

It is not recommended to continue driving your 2016 GMC Sierra with OBDII code P18B5 present, as it can lead to further damage to the transmission or other components. It is best to address the issue promptly to avoid potential safety hazards.

5. How can OBDII code P18B5 on a 2016 GMC Sierra be repaired?

Repairing OBDII code P18B5 may involve replacing the internal mode switch, repairing or replacing damaged wiring or connectors, or reprogramming the transmission control module. It is advisable to have the repairs done by a qualified technician.

6. Is it possible to reset OBDII code P18B5 on a 2016 GMC Sierra without fixing the underlying issue?

While you can clear the code temporarily using a scan tool, it will likely reappear if the underlying issue causing OBDII code P18B5 is not addressed. It is essential to fix the problem to prevent further complications.

7. How much does it typically cost to repair OBDII code P18B5 on a 2016 GMC Sierra?

The cost of repairing OBDII code P18B5 on a 2016 GMC Sierra can vary depending on the exact cause of the issue, labor rates in your area, and the cost of parts. It is best to obtain a diagnosis and repair estimate from a reputable repair shop.

8. Can a DIY enthusiast fix OBDII code P18B5 on a 2016 GMC Sierra?

While some experienced DIY enthusiasts may be able to diagnose and repair OBDII code P18B5, it is a complex issue related to the transmission system. It is recommended to seek professional help to ensure proper diagnosis and repair.

9. Will OBDII code P18B5 cause permanent damage to my 2016 GMC Sierra if left unresolved?

Leaving OBDII code P18B5 unresolved can potentially cause further damage to the transmission or other components over time. It is best to address the issue promptly to prevent costly repairs or safety risks.

10. How long does it typically take to repair OBDII code P18B5 on a 2016 GMC Sierra?

The repair time for OBDII code P18B5 on a 2016 GMC Sierra can vary depending on the exact cause of the issue and the availability of parts. It is advisable to consult with a mechanic for an accurate estimate of the repair timeline.