AutoCodes – Chevrolet – P1840 2015 Chevrolet Silverado

P1840 2015 Chevrolet Silverado Code - Internal Mode Switch 'S' Circuit Low 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: P1840 2015 Chevrolet Silverado indicates Internal Mode Switch 'S' Circuit Low 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 263

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 P1840 2015 Chevrolet Silverado 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 less than 0.7 V, for 1.75 s.

OBDII Code P1840 2015 Chevrolet Silverado - Internal Mode Switch 'S' Circuit Low Voltage - AutoCodes.com — P1840 2015 Chevrolet Silverado Code - Internal Mode Switch 'S' Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P1840 2015 Chevrolet Silverado?

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 P1840 2015 Chevrolet Silverado?

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 P1840 2015 Chevrolet Silverado 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 P1840 2015 Chevrolet Silverado code?

Need more information on how to fix the P1840 2015 Chevrolet Silverado 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 P1840 2015 Chevrolet Silverado Code

1. What does OBDII code P1840 mean for a 2015 Chevrolet Silverado?

The code P1840 indicates an issue with the Internal Mode Switch 'S' Circuit registering low voltage in a 2015 Chevrolet Silverado.

2. What are the common symptoms of OBDII code P1840 in a 2015 Chevrolet Silverado?

Common symptoms of code P1840 may include issues with shifting gears, erratic transmission behavior, and the check engine light illuminating on the dashboard.

3. What are the possible causes of OBDII code P1840 in a 2015 Chevrolet Silverado?

Potential causes of code P1840 include a faulty internal mode switch, damaged wiring or connectors in the circuit, or a malfunctioning transmission control module.

4. How can I diagnose OBDII code P1840 in my 2015 Chevrolet Silverado?

Diagnosing code P1840 may involve using a diagnostic scanner to retrieve the specific fault codes, inspecting the internal mode switch and related wiring, and testing the transmission control module.

5. Can I continue driving my 2015 Chevrolet Silverado with OBDII code P1840?

It is not recommended to continue driving with code P1840 present, as it can lead to further transmission issues and potential safety hazards. It is advisable to address the problem promptly.

6. How can I repair OBDII code P1840 in my 2015 Chevrolet Silverado?

Repairing code P1840 may involve replacing the internal mode switch, repairing any damaged wiring or connectors, or reprogramming the transmission control module as necessary.

7. Should I reset the fault codes after repairing OBDII code P1840 in my 2015 Chevrolet Silverado?

Once the underlying issue causing code P1840 has been resolved, it is recommended to clear the fault codes using a diagnostic scanner to reset the check engine light and ensure proper functionality.

8. Can a DIY enthusiast fix OBDII code P1840 in a 2015 Chevrolet Silverado?

While some aspects of diagnosing and repairing code P1840 may be within reach of experienced DIY enthusiasts, it is advisable to seek professional assistance, especially for complex transmission-related issues.

9. Is OBDII code P1840 a common problem in 2015 Chevrolet Silverado vehicles?

Code P1840 related to the Internal Mode Switch 'S' Circuit low voltage may occur in 2015 Chevrolet Silverado vehicles, but its frequency can vary depending on factors such as maintenance, driving habits, and vehicle age.

10. What is the typical cost to repair OBDII code P1840 in a 2015 Chevrolet Silverado?

The cost of repairing code P1840 can vary widely based on the specific cause of the issue, parts needed for replacement, labor costs, and whether the repair is done at a dealership or an independent mechanic.