P0078 OBD-II: Exhaust Valve Control Solenoid Circuit

OBD II Fault Code

• OBD II P0078

OBD-II Code Decreased engine performance is defined as a Exhaust Valve Control Solenoid Circuit

The Exhaust Valve Control Solenoid uses oil pressure and an electrical solenoid to control the position of the exhaust valve. Newer vehicles are equipped with variable valve timing (VVT). This allows the engine control module (PCM) to adjust the opening and closing of the exhaust valve to improve fuel consumption while still providing the performance requested by the driver. When the PCM determines there is an issue with the signal from the Exhaust Control Solenoid, the PCM will set code P0078.

Decreased engine performance Symptoms

• Decreased engine performance
• Engine may not start
• Increased fuel consumption

Common Problems That Trigger the P0078 Code

• Engine oil level is too low
• Exhaust valve control solenoid failure
• Powertrain Control Module (PCM) failure
• The engine oil does not meet the manufacturer's requirements
• Wiring issue

Common Repairs Needed for the P0078 Code

• Oil and Filter Change