AutoCodes – GMC – P0878 2016 GMC Sierra

P0878 2016 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 2016 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 193

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 2016 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 2016 GMC Sierra - Transmission Fluid Pressure Switch 4 Circuit High Voltage - AutoCodes.com — P0878 2016 GMC Sierra Code - Transmission Fluid Pressure Switch 4 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0878 2016 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 2016 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 2016 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 2016 GMC Sierra 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 2016 GMC Sierra Code

1. What does the OBDII code P0878 mean on a 2016 GMC Sierra?

P0878 indicates that the Transmission Fluid Pressure Switch 4 Circuit is experiencing high voltage, which typically points to an issue with the transmission pressure switch or related wiring.

2. What are the common symptoms of code P0878 in a 2016 GMC Sierra?

Common symptoms include harsh or erratic shifting, transmission slipping, the vehicle entering "limp mode," and the illumination of the check engine light.

3. What causes the P0878 code to appear on a GMC Sierra?

The most common causes are a faulty transmission fluid pressure switch, damaged or corroded wiring or connectors in the circuit, and occasionally, a problem with the transmission control module (TCM).

4. Can low transmission fluid cause the P0878 code on a GMC Sierra?

While low transmission fluid levels can affect overall transmission performance, the P0878 code specifically relates to an electrical issue in the pressure switch circuit, not fluid levels.

5. How do you diagnose the P0878 code on a 2016 GMC Sierra?

Diagnosis typically involves using a scan tool, inspecting the wiring and connectors for damage or corrosion, testing the transmission fluid pressure switch for proper operation, and checking the TCM for faults.

6. Can you drive with the P0878 code on a GMC Sierra?

Driving with this code is not recommended, as it may cause further transmission damage or result in unsafe driving conditions due to erratic shifting or limp mode.

7. How do you fix the P0878 code on a 2016 GMC Sierra?

Repairs may include replacing the faulty transmission fluid pressure switch, repairing or replacing damaged wiring or connectors, and in rare cases, reprogramming or replacing the TCM.

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

The repair cost can vary widely, ranging from $100-$300 for wiring or switch repairs to $500 or more if the TCM needs replacement or reprogramming.

9. Does the P0878 code always mean a bad transmission fluid pressure switch?

Not always. While the switch is a common culprit, wiring issues, connector problems, or a malfunctioning TCM can also trigger this code.

10. Can a dirty or contaminated transmission fluid cause the P0878 code?

Dirty or contaminated fluid is unlikely to directly cause the P0878 code, but it can contribute to other transmission problems that may indirectly affect pressure readings.