P0110: Intake Air Temperature Sensor 1 Circuit

P0110 means the engine control unit has found a fault in the intake air temperature (IAT) sensor circuit. Depending on the make it covers a reading that jumps between open and shorted, a circuit fault not split into high or low, or an internal error reported by a combined airflow and temperature sensor. The ECU then uses a substitute temperature, so the car usually drives normally or close to it. The cause is nearly always a connector, a wire or the sensor, which on many engines is built into the mass air flow sensor.

P0110 is a emissions-related diagnostic trouble code classified as low severity. When your vehicle's ECU detects this condition, it stores P0110 and illuminates the check engine light.

If your vehicle has triggered P0110, you may notice one or more of these symptoms:

• Check engine light on, often the only thing the driver notices
• Harder starting or a rough idle when the engine is cold
• Slightly higher fuel consumption
• Hesitation on acceleration, especially in very cold or very hot weather
• Live intake air temperature stuck at -40 degrees C, or showing an impossibly high value, on a scan tool
• Engine speed limited on some engines, where the ECU uses a rev cap as a fail-safe
• Mass air flow codes at the same time on engines where the IAT sensor is built into the MAF sensor

Here are the most common causes of P0110:

Generally yes, for short-term driving. Generally safe to drive. The ECU replaces the faulty reading with a substitute air temperature, so the engine keeps running, though cold starts, fuel consumption and throttle response can suffer. Some engines go further as a fail-safe and cap engine speed, so if the car will not rev out, drive it gently to a workshop. Book the repair soon rather than leaving it.

Follow these steps to pinpoint the root cause of P0110:

1. Read every stored code and the freeze frame. A generic OBD2 reader can do this and can show live intake air temperature, which is enough for most of the tests below. It cannot show a manufacturer's internal sensor error detail or run the manufacturer's own test routine, which needs manufacturer-level software. If several sensors report faults at once, suspect a shared sensor ground before any single sensor
2. With the engine cold and the ignition on, read the live intake air temperature. It should be close to the outside temperature. A reading of -40 degrees C means the ECU sees an open circuit; an impossibly high reading (Toyota uses 140 degrees C) means a short. A plausible reading that jumps while you wiggle the connector and harness is an intermittent contact
3. Find the sensor. It is either a separate sensor in the intake duct or air filter housing, or built into the mass air flow sensor. Check that the plug is fully home and locked, and look for corroded, pushed-back or bent pins, especially if the air filter was changed recently
4. On an analogue sensor (a separate one, or one built into an older air flow meter as on the second-generation Prius), test the wiring from the plug. With the sensor unplugged and the ignition on, the reading should fall to -40 degrees C. Then bridge the signal and ground pins on the harness side: the reading should jump to the hottest value. If both happen, the wiring and ECU are fine and the sensor is at fault. If the reading stays at -40 with the bridge fitted, a wire is open; if it stays hot with the sensor unplugged, the signal wire is shorted to ground
5. On a separate analogue sensor, measure its resistance. It is a thermistor whose resistance falls as it warms, typically around 2,000 to 3,000 ohms at 20 degrees C; an infinite reading means an open element. Compare with the figure in the manual for your engine
6. On engines where the MAF and IAT form one digital sensor, the sensor reports its own internal errors and cannot be checked with an ohmmeter. Follow the manufacturer's procedure, which checks fitting, connector and wiring before condemning the sensor
7. After the repair, clear the code, restart, and confirm the live temperature reads close to ambient and rises steadily as the engine bay warms up

Repair costs for P0110 vary depending on the root cause and your vehicle. Here are typical estimates:

P0110 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

These codes are often seen alongside P0110 or indicate related issues: