P0878 2018 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 2018 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.
Code P0878 2018 GMC Sierra Description
What are the Possible Causes of the DTC P0878 2018 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 2018 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 2018 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.
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Frequently Asked Questions about P0878 2018 GMC Sierra Code
1. What does the OBDII code P0878 mean on a 2018 GMC Sierra?
P0878 indicates that the Transmission Control Module (TCM) has detected high voltage in the Transmission Fluid Pressure Switch 4 circuit.
2. What are the common symptoms of code P0878 in a 2018 GMC Sierra?
Symptoms may include harsh shifting, slipping gears, the transmission stuck in one gear, or the Check Engine Light being illuminated.
3. What causes the P0878 code to appear in a 2018 GMC Sierra?
Common causes include a faulty pressure switch, damaged wiring or connectors in the circuit, a malfunctioning TCM, or low or contaminated transmission fluid.
4. Can low transmission fluid cause the P0878 code in a GMC Sierra?
Yes, low or contaminated transmission fluid can cause erratic pressure readings, leading to the P0878 code.
5. How do I fix the P0878 code on my 2018 GMC Sierra?
Repairs may include replacing the faulty pressure switch, repairing damaged wiring or connectors, flushing and refilling the transmission fluid, or reprogramming or replacing the TCM.
6. Is it safe to drive a 2018 GMC Sierra with the P0878 code?
It’s not recommended to drive with this code active, as it can lead to further transmission damage or unsafe driving conditions due to shifting issues.
7. How do you diagnose the P0878 code in a GMC Sierra?
Diagnosis typically involves scanning for other codes, visually inspecting the wiring and connectors, testing the pressure switch with a multimeter, and checking the transmission fluid condition.
8. Can a faulty Transmission Control Module (TCM) trigger the P0878 code?
Yes, a malfunctioning TCM can send incorrect signals or fail to interpret pressure switch data, triggering the P0878 code.
9. How much does it cost to fix the P0878 code on a 2018 GMC Sierra?
Repair costs can range from $150 to $500 or more, depending on whether the issue is with the pressure switch, wiring, or TCM.
10. Will clearing the P0878 code solve the problem in my GMC Sierra?
Clearing the code without addressing the underlying issue will not fix the problem, and the code is likely to reappear.
Discuss the causes and fixes for P0878 2018 GMC Sierra OBDII Code
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