P278B Engine Trouble Code
What is P278B?
When P278B code appears, first check your gas cap. Pull over safely, ensure it is tight, and inspect for cracks. A loose or damaged gas cap affects fuel-system pressure and emissions. A replacement cap costs about $3–$10. This simple fix can resolve the code and improve fuel economy.
Code Information
| Code Type: | OBD-II Powertrain (P) Trouble Code |
| System: | Powertrain |
| Code: | P278B |
P278B Symptoms
Check Engine Light
Illuminated dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration
Starting Problems
Difficulty starting the engine
P278B Code Structure
Understanding what each digit means in the P278B powertrain trouble code:
| P | 2 | 7 | 8 | b |
|---|---|---|---|---|
| Powertrain Code | Fuel And Air Metering (Injector Circuit Malfunctions Only) | Fuel Rail Pressure Sensor Circuit Malfunction | Ignition/Distributor Engine Speed Input Circuit Malfunction | System Malfunction |
How to Fix P278B
Diagnostic Steps:
Oxygen sensors measure exhaust gas oxygen content to optimise air-fuel ratio. This optimisation improves fuel economy and reduces emissions. Sensors degrade over time and require periodic replacement.
Repair Solution:
Firing order is engineered to minimise vibration. Altering firing order results in mistimed ignition and poor engine operation. Consult vehicle-specific repair manual for correct firing order.
Technical Notes:
P278B on electronically controlled automatic transmissions relates to shift solenoid operation. The solenoid actuates hydraulic circuits controlling clutches or bands for gear changes.
P278B Description
P278B engine trouble code is related to System Malfunction.
Main Cause
The primary reason for P278B OBD-II Engine Trouble Code is: Fuel Rail Pressure Sensor Circuit Malfunction.