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P1840 2014 Chevrolet Silverado Code - Internal Mode Switch 'S' Circuit Low Voltage

Quick Answer

The diagnostic trouble code P1840 on a 2014 Chevrolet Silverado indicates an issue with the Internal Mode Switch 'S' Circuit having low voltage. Common causes include Faulty Internal Mode Switch, Damaged or corroded wiring/connectors in the 'S' circuit, Issues with the transmission control module. 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 2014 Chevrolet Silverado indicates Internal Mode Switch 'S' Circuit Low Voltage.
Common causes
Common causes include Faulty Internal Mode Switch, Damaged or corroded wiring/connectors in the 'S' circuit, Issues with the transmission control module.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 12, 2024
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Code P1840 2014 Chevrolet Silverado Description

The diagnostic trouble code P1840 on a 2014 Chevrolet Silverado indicates an issue with the Internal Mode Switch 'S' Circuit having low voltage. The Internal Mode Switch (IMS) is a component of the transmission system that helps the Powertrain Control Module (PCM) to determine the requested gear position by the driver. The 'S' circuit specifically refers to the signal circuit that is responsible for reporting the position of the shift lever to the PCM.

OBDII Code P1840 2014 Chevrolet Silverado - Internal Mode Switch 'S' Circuit Low Voltage
P1840 2014 Chevrolet Silverado Code - Internal Mode Switch 'S' Circuit Low Voltage

Common Causes of P1840 2014 Chevrolet Silverado

  1. Faulty Internal Mode Switch
  2. Damaged or corroded wiring/connectors in the 'S' circuit
  3. Issues with the transmission control module
  4. Low battery voltage affecting the 'S' circuit
  5. PCM software issues

Symptoms of P1840 2014 Chevrolet Silverado

  1. Erratic shifting behavior
  2. Harsh or delayed gear shifts
  3. Transmission slipping
  4. Inability to shift gears
  5. Illumination of the Check Engine Light

How to Fix P1840 2014 Chevrolet Silverado

  1. Begin by conducting a thorough visual inspection of the wiring and connectors in the 'S' circuit to check for any damage or corrosion. Repair or replace any faulty wiring or connectors.
  2. Test the Internal Mode Switch using a multimeter to verify its functionality. Replace the IMS if it is found to be faulty.
  3. Check the battery voltage and ensure it is within the specified range. Low battery voltage can affect the 'S' circuit operation.
  4. If the issue persists, diagnose the transmission control module and PCM for any software-related issues. Update or reprogram the modules if necessary.
  5. Clear the diagnostic trouble codes from the PCM and test drive the vehicle to confirm that the issue has been resolved.

Cost to Fix P1840 2014 Chevrolet Silverado

The typical repair costs for addressing the Internal Mode Switch 'S' Circuit Low Voltage issue on a 2014 Chevrolet Silverado can range from $200 to $500, including parts and labor. This estimate may vary depending on the specific components that need to be replaced and the labor rates at the auto repair shop. It is advisable to consult with a professional mechanic to get an accurate cost estimate based on the individual circumstances of the vehicle. Labor rates at auto repair shops can vary, with most charging between $80 and $150 per hour, so it is recommended to inquire about the rates in your local area for a more precise estimate.

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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 2014 Chevrolet Silverado Code

1. What does OBDII code P1840 mean on a 2014 Chevrolet Silverado?

Code P1840 indicates that the Internal Mode Switch (IMS) 'S' circuit is experiencing low voltage, which can affect the transmission's ability to detect the correct gear position.

2. What are common symptoms of code P1840 in a 2014 Chevy Silverado?

Symptoms may include erratic shifting, the transmission stuck in one gear, the check engine light illuminated, and reduced vehicle performance.

3. What causes P1840 in a 2014 Chevrolet Silverado?

The most common causes include a faulty Internal Mode Switch, damaged wiring or connectors in the IMS circuit, or a transmission control module (TCM) issue.

4. Can I drive my 2014 Chevy Silverado with a P1840 code?

While the vehicle may still be drivable, continuing to drive with this code can lead to further transmission damage and unsafe driving conditions. It’s recommended to address the issue promptly.

5. How is P1840 diagnosed on a 2014 Chevrolet Silverado?

A mechanic will use a scan tool to confirm the code, inspect the IMS circuit for damaged wiring or poor connections, and test the IMS for proper operation.

6. How do you fix code P1840 on a 2014 Chevy Silverado?

Repairs may involve replacing the Internal Mode Switch, repairing or replacing damaged wiring or connectors, or reprogramming or replacing the transmission control module if necessary.

7. What is the Internal Mode Switch in a 2014 Chevy Silverado?

The Internal Mode Switch is a sensor in the transmission that communicates the gear position to the vehicle’s computer system to ensure proper operation.

8. How much does it cost to repair P1840 in a 2014 Chevrolet Silverado?

Repair costs can vary, but replacing the Internal Mode Switch typically ranges from $200 to $500, depending on labor rates and parts availability.

9. Can a low battery cause P1840 in a 2014 Chevy Silverado?

While unlikely, a weak or failing battery can sometimes contribute to electrical issues, including triggering low voltage-related codes like P1840.

10. Is P1840 a common issue in the 2014 Chevrolet Silverado?

P1840 is not a widespread issue but can occur over time, especially in vehicles with higher mileage or those exposed to harsh operating conditions.

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