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Engine-Codes – GMC – P0878 GMC

P0878 GMC Code - Transmission Fluid Pressure Switch 4 Circuit High Voltage

Quick Answer

The P0878 GMC code indicates an issue with the Transmission Fluid Pressure Switch 4 Circuit High Voltage. Common causes include Faulty transmission fluid pressure switch, Wiring issues in the 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
P0878 GMC indicates Transmission Fluid Pressure Switch 4 Circuit High Voltage.
Common causes
Common causes include Faulty transmission fluid pressure switch, Wiring issues in the 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 10, 2024
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Code P0878 GMC Description

The P0878 GMC code indicates an issue with the Transmission Fluid Pressure Switch 4 Circuit High Voltage. This means that the transmission control module has detected a higher than normal voltage coming from the transmission fluid pressure switch in circuit 4. The transmission fluid pressure switch is responsible for monitoring the hydraulic pressure within the transmission. When the voltage is too high, it can lead to various problems with the transmission's performance.

OBDII Code P0878 GMC - Transmission Fluid Pressure Switch 4 Circuit High Voltage
P0878 GMC Code - Transmission Fluid Pressure Switch 4 Circuit High Voltage

Common Causes of P0878 GMC

  1. Faulty transmission fluid pressure switch
  2. Wiring issues in the circuit
  3. Malfunctioning transmission control module
  4. Low transmission fluid levels
  5. Contaminated transmission fluid

Symptoms of P0878 GMC

  1. Harsh or delayed shifting
  2. Transmission slipping
  3. Transmission overheating
  4. Transmission warning light illuminated on the dashboard
  5. Engine stalling when shifting gears

How to Fix P0878 GMC

  1. Begin by checking the transmission fluid level and condition. Top off or change the fluid if necessary.
  2. Inspect the wiring and connections related to the transmission fluid pressure switch 4 circuit. Repair or replace any damaged wires or connectors.
  3. Test the transmission fluid pressure switch using a multimeter to determine if it is functioning properly. Replace it if needed.
  4. Clear the diagnostic trouble codes from the vehicle's computer using a scan tool.
  5. Test drive the vehicle to ensure the issue has been resolved and the code does not reappear.

Cost to Fix P0878 GMC

The typical repair costs for addressing the P0878 GMC code can range from $200 to $500, including parts and labor. However, it is important to note that specific diagnosis time and labor rates at auto repair shops can vary based on factors such as location, vehicle make and model, and engine type. It is recommended to check with local auto repair shops for a more accurate estimate. Labor rates generally range from $80 to $150 per hour, with higher rates in metropolitan areas or at dealerships and lower rates at independent shops.

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Information for Specific GMC Models

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 P0878 GMC Code

1. What are the common symptoms of OBDII code P0878 on a GMC vehicle?

The common symptoms of OBDII code P0878 include harsh shifting, erratic transmission behavior, transmission slippage, and illuminated warning lights on the dashboard.

2. What does the OBDII code P0878 on a GMC indicate?

OBDII code P0878 indicates a high voltage condition in Transmission Fluid Pressure Switch 4 Circuit, signaling a potential issue with the transmission fluid pressure control system.

3. What are the possible causes of OBDII code P0878 in a GMC vehicle?

Possible causes of OBDII code P0878 include a faulty transmission fluid pressure switch, wiring or connector issues, low transmission fluid level, or a malfunctioning transmission control module.

4. How can I diagnose the source of OBDII code P0878 on my GMC vehicle?

Diagnosing OBDII code P0878 involves checking the transmission fluid level, inspecting the wiring and connectors related to the pressure switch, and using a scan tool to monitor the switch's voltage readings.

5. Can I continue driving my GMC vehicle with OBDII code P0878 present?

It is not recommended to continue driving your GMC vehicle with OBDII code P0878 present, as it can lead to further damage to the transmission components and potentially result in more costly repairs.

6. How can I repair OBDII code P0878 in my GMC vehicle?

Repairing OBDII code P0878 may involve replacing the Transmission Fluid Pressure Switch 4 Circuit, repairing any damaged wiring or connectors, ensuring the correct transmission fluid level, and clearing the trouble code.

7. Is it possible to reset OBDII code P0878 on a GMC without fixing the underlying issue?

While it is possible to clear the trouble code temporarily, OBDII code P0878 will likely reappear if the root cause of the high voltage condition in the transmission fluid pressure switch is not addressed.

8. Can a DIY enthusiast fix OBDII code P0878 on a GMC, or is professional assistance required?

Depending on the individual's skill level and access to tools, a DIY enthusiast may be able to address OBDII code P0878 by following repair guides and utilizing proper diagnostic equipment. However, professional assistance is recommended for complex transmission-related issues.

9. How much does it typically cost to repair OBDII code P0878 in a GMC vehicle?

The cost of repairing OBDII code P0878 can vary based on the extent of the damage and the specific components needing replacement. Costs may range from a few hundred dollars for simple repairs to over a thousand dollars for more extensive transmission work.

10. Are there any preventive maintenance measures to help avoid OBDII code P0878 in a GMC vehicle?

Regularly checking and maintaining the transmission fluid level, addressing any leaks promptly, and ensuring the transmission system is serviced according to the manufacturer's recommendations can help prevent issues like OBDII code P0878 from occurring.

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