AutoCodes – GMC – P18BE 2018 GMC Sierra

P18BE 2018 GMC Sierra Code - Internal Mode Switch 'S' Circuit Stuck Off Invalid Voltage Range

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: P18BE 2018 GMC Sierra indicates Internal Mode Switch 'S' Circuit Stuck Off Invalid Voltage Range.
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 166

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 P18BE 2018 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 S signal circuit has an invalid voltage range of 1.68 – 2.38 V, for 2.7 s.

OBDII Code P18BE 2018 GMC Sierra - Internal Mode Switch 'S' Circuit Stuck Off Invalid Voltage Range - AutoCodes.com — P18BE 2018 GMC Sierra Code - Internal Mode Switch 'S' Circuit Stuck Off Invalid Voltage Range

What does this mean?

What are the Possible Causes of the DTC P18BE 2018 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 P18BE 2018 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 P18BE 2018 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 P18BE 2018 GMC Sierra code?

Need more information on how to fix the P18BE 2018 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 P18BE 2018 GMC Sierra Code

1. What does the OBDII code P18BE mean on a 2018 GMC Sierra?

The P18BE code indicates that the Internal Mode Switch 'S' Circuit is stuck off or has an invalid voltage range, often related to the transmission range sensor.

2. What are the common symptoms of the P18BE code in a 2018 GMC Sierra?

Symptoms can include difficulty shifting gears, the transmission being stuck in one gear, erratic shifting, or the illumination of the check engine light.

3. What causes the P18BE code to appear?

The code is commonly caused by a faulty internal mode switch, damaged wiring or connectors, or issues with the transmission control module (TCM).

4. Can a bad battery or low voltage trigger the P18BE code?

Yes, a weak or failing battery can cause voltage issues in the circuit and potentially trigger the P18BE code.

5. How is the P18BE code diagnosed?

A mechanic will typically perform a visual inspection of the wiring and connectors, use a diagnostic scanner to monitor live data, and test the internal mode switch and TCM for proper operation.

6. Can I drive my 2018 GMC Sierra with the P18BE code?

While it may be possible to drive, itâ€™s not recommended as the transmission may not function properly, potentially causing further damage or unsafe driving conditions.

7. How can the P18BE code be fixed on a 2018 GMC Sierra?

Repairs may include replacing the internal mode switch, repairing damaged wiring or connectors, or reprogramming or replacing the TCM if necessary.

8. How much does it cost to repair the P18BE code?

The cost varies depending on the exact cause, but replacing the internal mode switch typically costs between $200 and $500, plus labor.

9. Can the P18BE code be cleared without fixing the issue?

Clearing the code without addressing the underlying problem may temporarily turn off the check engine light, but the code is likely to return.

10. Is the P18BE code covered under warranty for a 2018 GMC Sierra?

It depends on your vehicleâ€™s warranty coverage. If the transmission or powertrain warranty is still active, it may cover repairs related to this code.