AutoCodes – GMC – P0878 2015 GMC Sierra

P0878 2015 GMC Sierra Code - Transmission Fluid Pressure Switch 4 Circuit High Voltage

Quick Answer

The Transmission Fluid Pressure (TFP) switch 4 is part of the Transmission Control Solenoid Valve Assembly which has no serviceable parts. Common causes include Low transmission fluid level, Dirty transmission fluid, Faulty Transmission Control Solenoid Valve Assembly. 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 2015 GMC Sierra indicates Transmission Fluid Pressure Switch 4 Circuit High Voltage.
Common causes: Common causes include Low transmission fluid level, Dirty transmission fluid, Faulty Transmission Control Solenoid Valve Assembly.
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.

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Code Popularity 219

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Aug 03, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0878 2015 GMC Sierra Description

The Transmission Fluid Pressure (TFP) switch 4 is part of the Transmission Control Solenoid Valve Assembly which has no serviceable parts. The Transmission Control Module (TCM) supplies a signal circuit to the TFP switch 4. The TFP switch 4 has an internal case ground. TFP switch 4 is normally closed or LOW. When oil pressure is present at the TFP switch 4, the switch is open or HIGH. The normal LOW pressure control solenoid 5 controls pressure to the 1-2-3-4 clutch regulator valve. The TCM monitors the TFP switch 4 to determine the position of the 1-2-3-4 clutch regulator valve. When the 1-2-3-4 clutch is commanded OFF, pressure is present on the TFP switch 4. When the 1-2-3-4 clutch is commanded ON, the 1-2-3-4 clutch regulator valve moves and pressure to the TFP switch 4 is exhausted through the 1-2-3-4 clutch regulator valve. The Diagnostic Trouble Code (DTC) will be set when the TCM detects that the TFP switch 4 signal voltage remains HIGH after the 1-2-3-4 clutch transitions from a LOW pressure state to a HIGH pressure state. The TCM counts each incident. The DTC sets when 8 counts are accumulated.

OBDII Code P0878 2015 GMC Sierra - Transmission Fluid Pressure Switch 4 Circuit High Voltage - AutoCodes.com — P0878 2015 GMC Sierra Code - Transmission Fluid Pressure Switch 4 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0878 2015 GMC Sierra?

Low transmission fluid level
Dirty transmission fluid
Faulty Transmission Control Solenoid Valve Assembly
Transmission Control Solenoid Valve Assembly harness is open or shorted
Transmission Control Solenoid Valve Assembly circuit poor electrical connection

How to Fix the DTC P0878 2015 GMC Sierra?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0878 2015 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0878 2015 GMC Sierra code?

Need more information on how to fix the P0878 2015 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0878 2015 GMC Sierra code diagnosed by a professional: Find a repair shop in your area

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 2015 GMC Sierra Code

1. What are common symptoms of OBDII code P0878 in a 2015 GMC Sierra?

Common symptoms include harsh shifting, transmission slipping, decreased fuel efficiency, and an illuminated Check Engine light.

2. What can cause OBDII code P0878 in a 2015 GMC Sierra?

The most common cause of code P0878 is a faulty transmission fluid pressure switch 4, high voltage in the transmission control module.

3. How can I diagnose OBDII code P0878 in my 2015 GMC Sierra?

To diagnose code P0878, a mechanic will typically use a scan tool to retrieve the code, inspect the transmission fluid pressure switch 4 and its circuit for any damage or malfunction.

4. Can I continue driving my 2015 GMC Sierra with OBDII code P0878?

It is not recommended to continue driving with code P0878 as it can lead to further damage to the transmission. It is best to address the issue promptly to avoid costly repairs.

5. How can I repair OBDII code P0878 in my 2015 GMC Sierra?

Repairing code P0878 usually involves replacing the faulty transmission fluid pressure switch 4 and clearing the code from the vehicle's memory using a scan tool.

6. Are there any DIY tips for fixing OBDII code P0878 in a 2015 GMC Sierra?

While it's recommended to have a professional diagnose and repair code P0878, DIYers with experience in automotive repairs can attempt to replace the transmission fluid pressure switch 4 themselves.

7. Will resetting the Check Engine light resolve OBDII code P0878 in my 2015 GMC Sierra?

Simply resetting the Check Engine light will not fix code P0878. The underlying issue causing the high voltage in the transmission fluid pressure switch 4 circuit needs to be addressed.

8. How much does it cost to repair OBDII code P0878 in a 2015 GMC Sierra?

The cost of repairing code P0878 can vary depending on the labor rates and parts pricing in your area. On average, the repair can range from $200 to $500.

9. Can bad transmission fluid cause OBDII code P0878 in a 2015 GMC Sierra?

While bad transmission fluid can affect the overall health of the transmission, it is not a common cause of code P0878. The issue is typically related to the transmission fluid pressure switch 4 circuit.

10. How long does it take to repair OBDII code P0878 in a 2015 GMC Sierra?

The repair time for code P0878 can vary depending on the mechanic's experience and workload. On average, the repair can take anywhere from 1 to 3 hours to complete.