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P0877 2018 GMC Sierra Code - Transmission Fluid Pressure Switch 4 Circuit Low Voltage

Quick Answer

The P0877 diagnostic trouble code (DTC) for a 2018 GMC Sierra refers to an issue with the Transmission Fluid Pressure Switch 4 Circuit, specifically indicating low voltage. Common causes include Faulty wiring or connectors in the transmission fluid pressure switch circuit, Malfunctioning transmission fluid pressure switch, Damaged transmission control module (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
P0877 2018 GMC Sierra indicates Transmission Fluid Pressure Switch 4 Circuit Low Voltage.
Common causes
Common causes include Faulty wiring or connectors in the transmission fluid pressure switch circuit, Malfunctioning transmission fluid pressure switch, Damaged transmission control module (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 17, 2024
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Code P0877 2018 GMC Sierra Description

The P0877 diagnostic trouble code (DTC) for a 2018 GMC Sierra refers to an issue with the Transmission Fluid Pressure Switch 4 Circuit, specifically indicating low voltage. This code is typically related to the transmission system and can have significant implications for the vehicle's performance and overall functionality. The transmission fluid pressure switch is responsible for monitoring and regulating the hydraulic pressure within the transmission system. When the voltage is detected to be low in Circuit 4, it can lead to various issues with the transmission's operation.

OBDII Code P0877 2018 GMC Sierra - Transmission Fluid Pressure Switch 4 Circuit Low Voltage
P0877 2018 GMC Sierra Code - Transmission Fluid Pressure Switch 4 Circuit Low Voltage

Common Causes of P0877 2018 GMC Sierra

  1. Faulty wiring or connectors in the transmission fluid pressure switch circuit
  2. Malfunctioning transmission fluid pressure switch
  3. Damaged transmission control module (TCM)
  4. Low transmission fluid level or contaminated fluid
  5. Electrical issues within the transmission system

Symptoms of P0877 2018 GMC Sierra

  1. Erratic shifting patterns
  2. Harsh shifting between gears
  3. Transmission slipping
  4. Decreased fuel efficiency
  5. Illumination of the Check Engine Light

How to Fix P0877 2018 GMC Sierra

  1. Begin by conducting a thorough inspection of the transmission fluid pressure switch circuit, checking for any loose connections or damaged wiring.
  2. Test the transmission fluid pressure switch to determine if it is functioning correctly. Replace the switch if necessary.
  3. Inspect the transmission control module (TCM) for any signs of damage or malfunction. Replace the TCM if it is found to be faulty.
  4. Check the transmission fluid level and quality, topping up or replacing the fluid as needed.
  5. Clear the DTC from the vehicle's computer system and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P0877 2018 GMC Sierra

The typical repair costs for addressing a P0877 code in a 2018 GMC Sierra can vary depending on the specific cause of the issue and the extent of the repairs needed. On average, the cost of parts for this repair can range from $100 to $300, while labor costs can range from $150 to $400. Overall, the total cost of addressing this issue can range from $250 to $700. It's important to note that these are rough estimates, and actual costs may vary based on factors such as location, vehicle make and model, and the repair shop's labor rates. It is advisable to consult with a qualified mechanic or repair shop to obtain a more accurate cost estimate for addressing the P0877 code in a 2018 GMC Sierra.

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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 P0877 2018 GMC Sierra Code

1. What does OBDII code P0877 mean on a 2018 GMC Sierra?

P0877 indicates that the Transmission Fluid Pressure Switch 4 circuit is experiencing low voltage, suggesting an electrical or mechanical issue with the pressure switch.

2. What are the symptoms of code P0877 on a 2018 GMC Sierra?

Common symptoms include erratic shifting, the transmission staying in limp mode, delayed gear engagement, and the check engine light being illuminated.

3. What causes code P0877 on a 2018 GMC Sierra?

Possible causes include a faulty transmission fluid pressure switch, damaged wiring or connectors in the circuit, low transmission fluid levels, or an issue with the transmission control module (TCM).

4. Can low transmission fluid cause code P0877?

Yes, low transmission fluid can lead to inadequate pressure, potentially triggering the P0877 code.

5. How do I diagnose code P0877 on my 2018 GMC Sierra?

Start by checking the transmission fluid level and condition, inspecting the wiring and connectors for damage, and testing the transmission fluid pressure switch with a multimeter.

6. Can I drive my 2018 GMC Sierra with code P0877 active?

It is not recommended, as driving with this issue can lead to further damage to the transmission and result in unsafe driving conditions.

7. How do I fix code P0877 on a 2018 GMC Sierra?

Repairs may involve replacing the faulty pressure switch, repairing or replacing damaged wiring, cleaning corroded connectors, or reprogramming/updating the TCM.

8. How much does it cost to repair code P0877 on a 2018 GMC Sierra?

The cost varies depending on the repair, but replacing a transmission fluid pressure switch typically costs $150–$300, while wiring repairs may vary based on labor.

9. Can a faulty TCM cause code P0877?

Yes, a malfunctioning TCM can misinterpret or fail to process signals from the pressure switch, potentially triggering the P0877 code.

10. Is a professional mechanic required to fix code P0877?

While some issues like checking fluid levels or inspecting wiring can be done at home, diagnosing and repairing electrical or transmission-related problems often requires professional expertise.

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