AutoCodes – Chevrolet – P1840 2017 Chevrolet Silverado

P1840 2017 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 2017 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 288

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 2017 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 2017 Chevrolet Silverado - Internal Mode Switch 'S' Circuit Low Voltage - AutoCodes.com — P1840 2017 Chevrolet Silverado Code - Internal Mode Switch 'S' Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P1840 2017 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 2017 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 2017 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 2017 Chevrolet Silverado code?

Need more information on how to fix the P1840 2017 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 2017 Chevrolet Silverado Code

1. What are the common symptoms of OBDII code P1840 in a 2017 Chevrolet Silverado?

The common symptoms of OBDII code P1840 in a 2017 Chevrolet Silverado include issues with shifting gears, hesitation or jerking during acceleration, and the inability to start the vehicle.

2. What does the OBDII code P1840 'Internal Mode Switch 'S' Circuit Low Voltage' indicate in a 2017 Chevrolet Silverado?

The OBDII code P1840 indicates a problem with the internal mode switch (IMS) 'S' circuit in a 2017 Chevrolet Silverado, specifically pointing to low voltage in the circuit.

3. What are the possible causes of OBDII code P1840 in a 2017 Chevrolet Silverado?

Possible causes of OBDII code P1840 in a 2017 Chevrolet Silverado include a faulty internal mode switch, damaged wiring or connectors in the circuit, low battery voltage, or a malfunctioning transmission control module.

4. How can I diagnose the Internal Mode Switch 'S' Circuit Low Voltage issue in my 2017 Chevrolet Silverado?

Diagnosing the Internal Mode Switch 'S' Circuit Low Voltage issue in a 2017 Chevrolet Silverado involves checking the internal mode switch for proper operation, inspecting the wiring and connectors for damage, testing the battery voltage, and scanning the transmission control module for related error codes.

5. Can I continue driving my 2017 Chevrolet Silverado with OBDII code P1840?

It is not recommended to continue driving your 2017 Chevrolet Silverado with OBDII code P1840, as it can lead to further transmission issues and potential safety hazards. It is best to address the problem promptly.

6. How can I repair OBDII code P1840 in a 2017 Chevrolet Silverado?

Repairing OBDII code P1840 in a 2017 Chevrolet Silverado may involve replacing the internal mode switch, repairing or replacing damaged wiring or connectors, ensuring proper battery voltage, and resetting the transmission control module.

7. Can a DIY enthusiast fix OBDII code P1840 in a 2017 Chevrolet Silverado?

While some aspects of diagnosing and repairing OBDII code P1840 may be tackled by a DIY enthusiast with the necessary tools and knowledge, it is recommended to seek professional help for accurate diagnosis and proper repair to avoid causing further damage.

8. How much does it typically cost to fix OBDII code P1840 in a 2017 Chevrolet Silverado?

The cost of fixing OBDII code P1840 in a 2017 Chevrolet Silverado can vary depending on the specific cause of the issue, parts needed for repair, and labor costs. It is advisable to obtain quotes from reputable mechanics or dealerships.

9. Will resetting the OBDII code P1840 clear the issue in my 2017 Chevrolet Silverado?

Resetting the OBDII code P1840 may temporarily clear the error code, but it will not fix the underlying issue causing the Internal Mode Switch 'S' Circuit Low Voltage problem in your 2017 Chevrolet Silverado. Proper diagnosis and repair are necessary.

10. How urgent is it to address OBDII code P1840 in a 2017 Chevrolet Silverado?

It is advisable to address OBDII code P1840 in a 2017 Chevrolet Silverado as soon as possible to prevent potential transmission problems and ensure the safety and proper functioning of your vehicle.