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P1839 2018 Chevrolet Silverado Code - Internal Mode Switch 'C' Circuit Low Voltage

Quick Answer

The P1839 diagnostic trouble code for a 2018 Chevrolet Silverado indicates an issue with the Internal Mode Switch 'C' Circuit Low Voltage. Common causes include Faulty internal mode switch, Damaged wiring or connectors in the circuit, Malfunctioning TCM. 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
P1839 2018 Chevrolet Silverado indicates Internal Mode Switch 'C' Circuit Low Voltage.
Common causes
Common causes include Faulty internal mode switch, Damaged wiring or connectors in the circuit, Malfunctioning TCM.
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 11, 2024
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Code P1839 2018 Chevrolet Silverado Description

The P1839 diagnostic trouble code for a 2018 Chevrolet Silverado indicates an issue with the Internal Mode Switch 'C' Circuit Low Voltage. The internal mode switch is responsible for providing feedback to the vehicle's transmission control module (TCM) regarding the position of the gear selector. This information is crucial for the TCM to determine the appropriate gear selection and shifting strategies. When the circuit voltage is detected to be lower than expected, it can lead to erratic shifting behavior, transmission slippage, or even the transmission not engaging at all.

OBDII Code P1839 2018 Chevrolet Silverado - Internal Mode Switch 'C' Circuit Low Voltage
P1839 2018 Chevrolet Silverado Code - Internal Mode Switch 'C' Circuit Low Voltage

Common Causes of P1839 2018 Chevrolet Silverado

  1. Faulty internal mode switch
  2. Damaged wiring or connectors in the circuit
  3. Malfunctioning TCM
  4. Corrosion or debris in the circuit
  5. Electrical issues such as a short circuit

Symptoms of P1839 2018 Chevrolet Silverado

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

How to Fix P1839 2018 Chevrolet Silverado

  1. Begin by conducting a thorough diagnosis using a scan tool to confirm the P1839 code and pinpoint the exact cause of the issue.
  2. Inspect the internal mode switch for any signs of damage or wear. Replace the switch if necessary.
  3. Check the wiring and connectors in the circuit for any damage, corrosion, or loose connections. Repair or replace as needed.
  4. Test the TCM functionality to ensure it is operating correctly. Replace the TCM if it is found to be faulty.
  5. Clear the trouble codes from the vehicle's computer after completing the repairs and test drive the vehicle to confirm that the issue has been resolved.

Cost to Fix P1839 2018 Chevrolet Silverado

The typical repair costs for addressing the Internal Mode Switch 'C' Circuit Low Voltage issue can vary depending on the specific cause of the problem. On average, the parts for this repair may range from $100 to $300, while the labor costs could amount to $150 to $400. It's important to note that diagnostic time and labor rates at auto repair shops can fluctuate, so it's advisable to consult with a professional to get an accurate estimate based on your location and vehicle specifics.

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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 P1839 2018 Chevrolet Silverado Code

1. What does OBDII code P1839 mean on a 2018 Chevrolet Silverado?

P1839 indicates an "Internal Mode Switch 'C' Circuit Low Voltage," meaning the transmission control module (TCM) has detected a low voltage signal from the Internal Mode Switch (IMS) circuit 'C.'

2. What are the symptoms of code P1839 in a 2018 Chevy Silverado?

Common symptoms include the transmission being stuck in one gear, harsh shifting, the vehicle going into limp mode, or the check engine light being illuminated.

3. What causes the P1839 code on a 2018 Chevrolet Silverado?

The most common causes include a faulty Internal Mode Switch, damaged or corroded wiring or connectors, low transmission fluid, or a malfunctioning TCM.

4. How do I diagnose the P1839 code in my Silverado?

Start by checking the transmission fluid level and inspecting the IMS circuit wiring and connectors for damage or corrosion. Use a multimeter to test for proper voltage and continuity in the IMS circuit.

5. Can I drive my 2018 Silverado with the P1839 code?

It is not recommended to drive with this code, as the transmission may not shift properly, potentially causing further damage or unsafe driving conditions.

6. How do I fix a P1839 code on a 2018 Chevrolet Silverado?

Repairs may include replacing the Internal Mode Switch, repairing or replacing damaged wiring or connectors, or reprogramming/replacing the TCM if necessary.

7. Does the P1839 code require a TCM replacement?

Not always. While a faulty TCM can cause this code, most cases are resolved by repairing wiring or replacing the Internal Mode Switch.

8. How much does it cost to fix the P1839 code on a Silverado?

The repair cost can vary widely, ranging from $50 for simple wiring repairs to $1,000 or more if the TCM or Internal Mode Switch needs replacement.

9. Can low transmission fluid trigger the P1839 code?

Yes, low or contaminated transmission fluid can affect the operation of the Internal Mode Switch and lead to this code being set.

10. Is the P1839 code a common issue for 2018 Chevrolet Silverado trucks?

While not extremely common, it can occur, particularly in vehicles with high mileage or those exposed to harsh driving conditions.

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