Intake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage
Your engine's air temperature sensor is sending weak electrical signals that come and go, like a loose connection flickering on and off. The computer can't reliably read how hot the incoming air is, which throws off fuel calculations.
The ECU monitors the IAT sensor's voltage output to determine intake air temperature, typically ranging from 0.2V to 4.7V as temperature changes. When voltage dips below the expected minimum threshold intermittently, the ECU logs a low-voltage fault. The sensor resistance increases as air temperature decreases, causing voltage drops that trigger this code when connections are loose or corroded.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| IAT Sensor Voltage | 0.5V to 4.5V (temperature dependent) | Below 0.2V intermittently or sustained low signal |
| Air Temperature Range | -40°C to +125°C | Reading below -40°C or erratic fluctuations |
Code P1117 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, P1117 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.