What does it mean?
Forced induction is used to improve power output and cruising fuel economy for a given engine displacement. Basically, exhaust gases rushing out the tailpipe are routed through a compressor, which compresses air going into the intake. The compressed air has more oxygen per given volume – more oxygen uses more fuel – the total result of which is power output on par with a larger-displacement engine.
When extra power isn’t needed, such as while idling or cruising, engine operation, power output, and efficiency match what the engine displacement might suggest, because the turbocharger isn’t active. Modern engines, controlled by the ECM (engine control module), use a number of sensors and actuators to fine-tune turbocharger function, which improves power output and fuel economy.
In the exhaust, between the cylinders and the turbocharger, the exhaust pressure sensor (EPS) continuously monitors pressure. Depending on application, the ECM uses EPS to monitor turbocharger function and control the turbocharger wastegate and boost pressure. Other automakers use EPS to monitor the capacity of the diesel particulate filter (DPF) in diesel applications.
Different automakers may call this differently, such as Ford (exhaust backpressure sensor – EBP) and Volkswagen (diesel particulate filter pressure differential sensor). If the ECM detects a problem with the EPS or its circuit, such as excessive pressure or abnormally-high voltage, usually over 4.7 V (58 psi), it will set a diagnostic trouble code (DTC) in system memory and illuminate the MIL (malfunction indicator lamp).
DTC P0473 is defined as “Exhaust Pressure Sensor High,” which may indicate a problem in the sensor or its circuit.