Ambient Air Temperature Sensor Circuit High Input
Your car's ambient air temperature sensor is reading a value that's too high, like a thermometer stuck on an unrealistic hot reading. The ECU uses this sensor to adjust fuel mixture and emissions controls, so a bad reading throws off these calculations.
The ECU monitors the ambient air temperature sensor voltage to detect outside air conditions. When the sensor circuit voltage exceeds the maximum threshold (typically above 4.8V), the ECU interprets this as an implausibly high temperature and sets a fault code. This helps the ECU adjust fuel trim, ignition timing, and emission control strategies.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sensor Voltage | 0.5V to 4.8V (-40°C to +125°C equivalent) | Above 4.8V (open circuit or high resistance condition) |
| Temperature Reading | -40°C to +125°C | Above +125°C (implausible high temperature) |
Code P0073 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, P0073 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.