P0478 Exhaust Pressure Control Valve High
P0478 is a diagnostic trouble code related to the exhaust pressure control valve circuit. The exhaust pressure control valve is responsible for regulating the exhaust gas recirculation system (EGR) pressure. The EGR system recirculates a portion of the exhaust gases back into the engine's intake system to reduce emissions. When the engine control module (ECM) detects that the exhaust pressure control valve is sending a high signal, it will store the P0478 diagnostic trouble code and illuminate the check engine light. This indicates that there is an issue with the exhaust pressure control valve circuit, which could result in decreased engine performance and increased emissions. To diagnose and repair this issue, a technician will need to perform a series of tests to determine the cause of the problem. They may start by checking the wiring and connections for the exhaust pressure control valve, as well as the valve itself, to make sure they are functioning properly. If the ...