AutoCodes – GMC – P1838 2016 GMC Sierra

P1838 2016 GMC Sierra Code - Internal Mode Switch 'A' Circuit High Voltage

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: P1838 2016 GMC Sierra indicates Internal Mode Switch 'A' Circuit High Voltage.
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 168

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 P1838 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 greater than 2.38 V, for 1.75 s.

OBDII Code P1838 2016 GMC Sierra - Internal Mode Switch 'A' Circuit High Voltage - AutoCodes.com — P1838 2016 GMC Sierra Code - Internal Mode Switch 'A' Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P1838 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 P1838 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 P1838 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 P1838 2016 GMC Sierra code?

Need more information on how to fix the P1838 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 P1838 2016 GMC Sierra Code

1. What are the common symptoms of OBDII code P1838 in a 2016 GMC Sierra?

- Common symptoms include issues with shifting gears, erratic behavior of the transmission, and the check engine light being illuminated.

2. What does the OBDII code P1838 'Internal Mode Switch 'A' Circuit High Voltage' mean in a 2016 GMC Sierra?

- This code indicates that there is a high voltage condition detected in the internal mode switch 'A' circuit of the transmission range sensor.

3. What are the possible causes of OBDII code P1838 in a 2016 GMC Sierra?

- Possible causes of this code include a faulty internal mode switch, damaged wiring or connectors in the circuit, or a malfunctioning transmission range sensor.

4. How can I diagnose OBDII code P1838 in a 2016 GMC Sierra?

- Diagnosing this code typically involves using a scan tool to retrieve the specific code, checking the internal mode switch and related wiring for any visible damage, and testing the transmission range sensor.

5. Can I still drive my 2016 GMC Sierra with OBDII code P1838 present?

- It is not recommended to continue driving the vehicle with this code present, as it can lead to further transmission issues and potentially cause damage if not addressed promptly.

6. How can I repair OBDII code P1838 in a 2016 GMC Sierra?

- Repairing this code usually involves replacing the internal mode switch, repairing any damaged wiring or connectors, or replacing the transmission range sensor if necessary.

7. Is it possible to reset OBDII code P1838 in a 2016 GMC Sierra without fixing the underlying issue?

- While you can clear the code with a scan tool, it is important to address the underlying issue causing the code to prevent further transmission problems.

8. Are there any DIY tips for troubleshooting OBDII code P1838 in a 2016 GMC Sierra?

- DIY tips include checking the transmission fluid level, inspecting the wiring and connectors for any visible damage, and ensuring all connections are secure.

9. How much does it typically cost to repair OBDII code P1838 in a 2016 GMC Sierra?

- The cost of repairing this code can vary depending on the specific issue, but it may range from $200 to $500 for parts and labor.

10. Can a mechanic easily fix OBDII code P1838 in a 2016 GMC Sierra?

- A qualified mechanic should be able to diagnose and repair this code efficiently, ensuring proper functioning of the transmission system in your GMC Sierra.