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P1839 2017 GMC Sierra Code - Internal Mode Switch 'C' Circuit Low Voltage

Quick Answer

The P1839 diagnostic trouble code (DTC) for a 2017 GMC Sierra indicates an issue with the Internal Mode Switch 'C' Circuit having low voltage. Common causes include Faulty Internal Mode Switch, Damaged wiring or connectors in the IMS circuit, Malfunctioning 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
P1839 2017 GMC Sierra indicates Internal Mode Switch 'C' Circuit Low Voltage.
Common causes
Common causes include Faulty Internal Mode Switch, Damaged wiring or connectors in the IMS circuit, Malfunctioning 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 17, 2024
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Code P1839 2017 GMC Sierra Description

The P1839 diagnostic trouble code (DTC) for a 2017 GMC Sierra indicates an issue with the Internal Mode Switch 'C' Circuit having low voltage. The Internal Mode Switch (IMS) is a component of the transmission control system that communicates the gear selector position to the vehicle's onboard computer. In this case, the 'C' circuit refers to a specific circuit within the IMS.

OBDII Code P1839 2017 GMC Sierra - Internal Mode Switch 'C' Circuit Low Voltage
P1839 2017 GMC Sierra Code - Internal Mode Switch 'C' Circuit Low Voltage

Common Causes of P1839 2017 GMC Sierra

  1. Faulty Internal Mode Switch
  2. Damaged wiring or connectors in the IMS circuit
  3. Malfunctioning transmission control module
  4. Electrical issues such as a blown fuse or relay
  5. Corrosion or moisture in the IMS circuit

Symptoms of P1839 2017 GMC Sierra

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

How to Fix P1839 2017 GMC Sierra

  1. Use a diagnostic scanner to retrieve the trouble code and confirm the issue.
  2. Inspect the Internal Mode Switch and its wiring for any visible damage or corrosion.
  3. Test the voltage in the IMS 'C' circuit to determine if it is within the specified range.
  4. Replace the Internal Mode Switch if it is found to be faulty.
  5. Clear the DTC and test drive the vehicle to ensure proper transmission operation.

Cost to Fix P1839 2017 GMC Sierra

The cost of repairing the Internal Mode Switch 'C' Circuit Low Voltage issue can vary depending on the specific cause of the problem and the labor rates in your area. Typically, replacing the Internal Mode Switch itself can range from $150 to $300, while diagnostic time and labor costs can add another $100 to $200. Overall, you can expect the total repair cost to be in the range of $250 to $500. It's recommended to consult with a qualified mechanic or repair shop to get an accurate estimate based on your vehicle's make and model. Keep in mind that labor rates can vary, so it's advisable to shop around for the best deal.

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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 2017 GMC Sierra Code

1. What are the common symptoms of OBDII code P1839 in a 2017 GMC Sierra?

The common symptoms of OBDII code P1839 (Internal Mode Switch 'C' Circuit Low Voltage) in a 2017 GMC Sierra may include issues with shifting gears, erratic transmission behavior, and a malfunction indicator light (MIL) on the dashboard.

2. What are the possible causes of OBDII code P1839 in a 2017 GMC Sierra?

Possible causes of OBDII code P1839 in a 2017 GMC Sierra include a faulty internal mode switch, damaged wiring or connectors in the circuit, low voltage in the switch circuit, or a malfunctioning transmission control module (TCM).

3. How can I diagnose OBDII code P1839 in my 2017 GMC Sierra?

To diagnose OBDII code P1839 in a 2017 GMC Sierra, you can use a diagnostic scanner to read the code and perform a thorough inspection of the internal mode switch, wiring, and connectors. Testing the voltage in the circuit and checking for any visible signs of damage can help pinpoint the issue.

4. Can I continue driving my 2017 GMC Sierra with OBDII code P1839?

It is not recommended to continue driving your 2017 GMC Sierra with OBDII code P1839, as it can lead to further transmission problems and potential safety hazards. It is advisable to address the issue promptly to avoid more significant damage.

5. How do I repair OBDII code P1839 in my 2017 GMC Sierra?

Repairing OBDII code P1839 in a 2017 GMC Sierra may involve replacing the internal mode switch, repairing or replacing damaged wiring or connectors, checking and correcting the voltage in the circuit, or reprogramming the transmission control module (TCM) if necessary.

6. Can a DIY enthusiast fix OBDII code P1839 in a 2017 GMC Sierra?

While some DIY enthusiasts may be able to diagnose and repair OBDII code P1839 in a 2017 GMC Sierra, it is recommended to seek professional help, especially when dealing with transmission-related issues. Proper diagnosis and repair are crucial to ensure the problem is addressed correctly.

7. Is OBDII code P1839 a serious issue in a 2017 GMC Sierra?

OBDII code P1839 (Internal Mode Switch 'C' Circuit Low Voltage) in a 2017 GMC Sierra should be taken seriously, as it can affect the transmission's performance and reliability. Ignoring this code can lead to transmission problems and potentially costly repairs if not addressed promptly.

8. How much does it cost to fix OBDII code P1839 in a 2017 GMC Sierra?

The cost to fix OBDII code P1839 in a 2017 GMC Sierra can vary depending on the root cause of the issue, the extent of the repairs needed, and labor costs. It is advisable to get a diagnostic assessment from a qualified mechanic to determine the exact cost.

9. Can OBDII code P1839 in a 2017 GMC Sierra cause other problems if left untreated?

If left untreated, OBDII code P1839 in a 2017 GMC Sierra can potentially cause further damage to the transmission system, leading to more severe issues such as transmission slippage, harsh shifting, or total transmission failure. It is essential to address this code promptly to prevent additional problems.

10. How long does it take to repair OBDII code P1839 in a 2017 GMC Sierra?

The time it takes to repair OBDII code P1839 in a 2017 GMC Sierra can vary depending on the exact cause of the issue, the availability of parts, and the mechanic's expertise. In general, repairs for this code can take a few hours to a full day to complete.

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