AutoCodes – GMC – P0878 2014 GMC Sierra

P0878 2014 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 2014 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 316

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 2014 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 2014 GMC Sierra - Transmission Fluid Pressure Switch 4 Circuit High Voltage - AutoCodes.com — P0878 2014 GMC Sierra Code - Transmission Fluid Pressure Switch 4 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0878 2014 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 2014 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 2014 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 2014 GMC Sierra code?

Need more information on how to fix the P0878 2014 GMC Sierra code? Get Access to Factory Service Manuals

Need Help with the Code?

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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 P0878 2014 GMC Sierra Code

1. What does the OBDII code P0878 mean on a 2014 GMC Sierra?

P0878 indicates a "Transmission Fluid Pressure Switch 4 Circuit High Voltage," meaning the transmission control module (TCM) has detected an abnormally high voltage signal from the transmission fluid pressure sensor for circuit 4.

2. What are the common symptoms of code P0878 in a 2014 GMC Sierra?

Symptoms may include harsh or delayed shifting, slipping gears, the transmission being stuck in one gear (limp mode), illuminated check engine light, and reduced fuel efficiency.

3. What causes the P0878 code to appear in my GMC Sierra?

Common causes include a faulty transmission fluid pressure sensor, damaged or corroded wiring or connectors in the circuit, a malfunctioning TCM, or low or contaminated transmission fluid.

4. Can low transmission fluid cause the P0878 code?

Yes, low or contaminated transmission fluid can affect the pressure sensor readings and trigger the P0878 code.

5. How do I diagnose the P0878 code on my 2014 GMC Sierra?

Start by inspecting the transmission fluid level and condition, checking for damaged wiring or connectors in the pressure switch circuit, and testing the transmission fluid pressure sensor with a multimeter.

6. Is it safe to drive with the P0878 code on my GMC Sierra?

Driving with this code is not recommended, as it may lead to poor transmission performance, additional damage, or unsafe driving conditions.

7. How do I fix the P0878 code on a 2014 GMC Sierra?

Repairs may include replacing the transmission fluid pressure sensor, repairing or replacing damaged wiring, cleaning corroded connectors, or reprogramming or replacing the TCM if necessary.

8. How much does it cost to repair the P0878 code on a GMC Sierra?

The cost varies depending on the issue. Replacing a transmission fluid pressure sensor typically costs $150â€“$300, while more extensive TCM repairs or wiring fixes can cost more.

9. Can a bad transmission control module (TCM) cause the P0878 code?

Yes, a malfunctioning TCM can send or interpret incorrect signals from the pressure sensor circuit, leading to the P0878 code.

10. Will resetting the code fix the P0878 issue on my GMC Sierra?

Clearing the code without addressing the underlying issue will not fix the problem, and the code is likely to return. Proper diagnosis and repair are necessary for a permanent solution.