AutoCodes – Buick – P0878 Buick

P0878 Buick 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 Buick 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 397

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 Buick 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 Buick - Transmission Fluid Pressure Switch 4 Circuit High Voltage - AutoCodes.com — P0878 Buick Code - Transmission Fluid Pressure Switch 4 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0878 Buick?

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 Buick?

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 Buick 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.

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Need Help with the Code?

Get the P0878 Buick 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 Buick Code

1. What are the common symptoms of OBDII code P0878 in a Buick related to the transmission fluid pressure switch 4 circuit high voltage?

The common symptoms include harsh shifting, transmission slipping, decreased fuel efficiency, and the transmission going into limp mode.

2. What are the possible causes of OBDII code P0878 in a Buick?

Possible causes include a faulty transmission fluid pressure switch, wiring issues, low transmission fluid levels, a malfunctioning transmission control module, or a problem with the transmission fluid pressure sensor circuit.

3. How can I diagnose OBDII code P0878 in my Buick related to the transmission fluid pressure switch 4 circuit high voltage?

Diagnosis typically involves using a scan tool to read the code, checking the transmission fluid level and condition, inspecting the wiring and connectors related to the pressure switch, and testing the pressure switch itself.

4. Can I continue driving my Buick with OBDII code P0878 present?

It is not recommended to drive with this code present, as it can lead to further damage to the transmission and potentially cause safety issues. It's best to address the issue promptly.

5. How can I repair OBDII code P0878 in my Buick?

Repair options may include replacing the transmission fluid pressure switch, repairing any damaged wiring or connectors, ensuring proper transmission fluid levels, and resetting the trouble code using a scan tool after the repair is completed.

6. Will resetting the trouble code make OBDII code P0878 go away permanently?

Resetting the trouble code may temporarily clear the code, but if the underlying issue causing the code is not addressed, it is likely to return. It's important to diagnose and repair the root cause of the problem.

7. Is it possible for a DIY enthusiast to fix OBDII code P0878 in a Buick?

While some basic diagnostic steps can be performed by DIY enthusiasts, diagnosing and repairing transmission-related issues can be complex. It is recommended to consult a professional mechanic for proper diagnosis and repair.

8. How much does it typically cost to repair OBDII code P0878 in a Buick?

The cost of repair can vary depending on the underlying cause of the code, the specific model of Buick, and labor rates in your area. It's best to get a diagnostic from a mechanic to determine the exact cost.

9. Can a faulty transmission fluid pressure switch cause other transmission problems in a Buick?

Yes, a faulty transmission fluid pressure switch can cause a range of transmission issues beyond just triggering OBDII code P0878, including erratic shifting, gear slippage, and transmission overheating.

10. How important is it to address OBDII code P0878 promptly in a Buick?

It is crucial to address this code promptly to prevent further damage to the transmission and ensure the safe operation of your vehicle. Ignoring this code can lead to more extensive and costly repairs down the line.