OBD-II code P0473 indicates that the engine computer has detected an abnormally high voltage in the exhaust pressure sensor circuit. This typically points to an electrical issue such as a short to power or a failing sensor, rather than an actual overpressure condition in the exhaust system.
The internal electronics of the sensor can fail, causing it to send a constant high-voltage signal to the PCM regardless of actual exhaust pressure.
A short to voltage, corroded terminals, or a disconnected wiring harness can cause the PCM to detect an abnormally high circuit voltage.
Soot or carbon buildup in the tube connecting the exhaust to the sensor can trap pressure and skew sensor readings, though this is less likely to cause a pure high-voltage circuit code than an electrical issue.
An exhaust leak near the sensor port can alter pressure readings, though this typically causes erratic readings rather than a consistently high circuit voltage.
An internal failure in the PCM is extremely rare and should only be considered after all wiring, sensor, and physical exhaust components are thoroughly verified.
No, replacing the PCM is almost never the correct fix for P0473. Mechanics frequently misdiagnose this code as a PCM failure, but it is overwhelmingly caused by a bad sensor, a wiring issue, or a blocked tube.
It depends. While the vehicle may run, it could enter limp mode to protect the engine, and the exhaust brake (if equipped) may fail, making it unsafe or impractical for heavy towing.
Not usually. A 'circuit high' code refers to the electrical voltage in the sensor circuit being higher than the normal range, which is typically an electrical fault rather than a physical overpressure condition.
It is far more common on diesel engines, which use exhaust pressure sensors to control the exhaust brake and monitor diesel particulate filter (DPF) function.