AutoCodes – GMC – P1841 2018 GMC Sierra

P1841 2018 GMC Sierra Code - Internal Mode Switch 'S' 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: P1841 2018 GMC Sierra indicates Internal Mode Switch 'S' 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 160

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 P1841 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 voltage is greater than 2.38 V, for 1.75 s.

OBDII Code P1841 2018 GMC Sierra - Internal Mode Switch 'S' Circuit High Voltage - AutoCodes.com — P1841 2018 GMC Sierra Code - Internal Mode Switch 'S' Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P1841 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 P1841 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 P1841 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 P1841 2018 GMC Sierra code?

Need more information on how to fix the P1841 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 P1841 2018 GMC Sierra Code

1. What are common symptoms of OBDII code P1841 in a 2018 GMC Sierra?

- Common symptoms include issues with shifting gears, the transmission not engaging properly, and the vehicle going into limp mode.

2. What causes the Internal Mode Switch 'S' Circuit High Voltage code in a 2018 GMC Sierra?

- The code P1841 is typically triggered by a faulty internal mode switch or wiring issues related to the switch.

3. How can I diagnose the Internal Mode Switch issue in my 2018 GMC Sierra?

- You can diagnose the internal mode switch by inspecting the wiring harness, checking for loose connections, and using a multimeter to test the switch's voltage output.

4. Can a DIYer repair OBDII code P1841 in a 2018 GMC Sierra?

- While some DIYers may be able to address this issue by replacing the internal mode switch or repairing wiring, it is recommended to consult a professional mechanic for accurate diagnosis and repair.

5. Are there any temporary fixes for the Internal Mode Switch 'S' Circuit High Voltage code?

- Resetting the vehicle's ECU by disconnecting the battery for a few minutes may temporarily clear the code, but the underlying issue should still be addressed to avoid further problems.

6. Will driving with OBDII code P1841 harm my 2018 GMC Sierra?

- Continuously driving with this code may lead to further transmission issues or failures, so it's best to address the problem as soon as possible to prevent damage.

7. How much does it cost to repair OBDII code P1841 in a 2018 GMC Sierra?

- The cost of repairing this code can vary depending on the specific issue causing it, but it may range from a couple of hundred dollars for parts and labor to over a thousand for more extensive repairs.

8. Can a bad battery cause the Internal Mode Switch 'S' Circuit High Voltage code?

- While a bad battery can potentially cause electrical issues in a vehicle, OBDII code P1841 is more commonly related to problems with the internal mode switch or its circuitry.

9. Is it safe to drive my 2018 GMC Sierra with the Internal Mode Switch 'S' Circuit High Voltage code illuminated?

- It is generally not recommended to drive the vehicle with this code active, as it can affect the transmission's performance and potentially lead to safety issues on the road.

10. How long does it take to repair OBDII code P1841 in a 2018 GMC Sierra?

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