Exhaust Pressure Sensor Low
Your exhaust pressure sensor is reading lower pressure than expected, like a tire pressure gauge stuck at 5 PSI when it should read 20 PSI. The engine computer can't properly monitor exhaust backpressure, which affects emissions control and engine performance.
The ECM monitors the exhaust pressure sensor voltage to ensure adequate backpressure in the exhaust system, typically 0.5–5 V corresponding to 0–10 PSI. A low signal (below ~0.3 V) indicates the sensor is reading near zero pressure, triggering the fault. This helps the ECM manage EGR flow and detect exhaust leaks or sensor degradation.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sensor Voltage | 0.5–5.0 V (0–10 PSI equivalent) | Below 0.3 V (near 0 PSI) |
| Exhaust Pressure | 2–8 PSI at idle/cruise | Below 0.5 PSI sustained |
Code P0473 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0473 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.