O2 Sensor Circuit High Voltage (Bank 1 Sensor 3)
Your downstream oxygen sensor (after the catalytic converter) is sending a signal that's too high, like a broken volume knob stuck at maximum. The engine computer expects this sensor to fluctuate between certain voltage levels, but it's staying pegged high.
The downstream O2 sensor produces a voltage signal (0.1–0.9V) that indicates exhaust oxygen content. The ECU monitors this voltage and expects it to toggle between rich and lean states. If voltage remains consistently high (above 0.8V), the ECU detects a fault—indicating either a wiring short, failed sensor, or exhaust leak upstream.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| O2 Sensor Voltage (Bank 1, Sensor 3) | 0.1–0.9V, oscillating | Sustained >0.8V (high voltage condition) |
| Signal Response Time | Quick transitions between states | Slow or no voltage change detected |
Code P0145 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, P0145 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.