P0112
Intake Air Temperature Sensor 1 Circuit Low
The appearance of the standard OBD2 trouble fault code P0112 is an indicator that your vehicle ECU triggered a threshold alert for "Intake Air Temperature Sensor 1 Circuit Low". Understanding the root component breakdown helps avoid expensive diagnostic fees.
Driver's Summary
Storing code P0112 is your car's way of telling you something is wrong with the intake air temperature sensor 1 circuit low. In practice, this fault causes hard starting when cold, poor gas mileage, rich exhaust. While the car is usually drivable, you should schedule a diagnosis within the next few days to prevent the issue from worsening.
Symptoms
Hard starting when cold, poor gas mileage, rich exhaust
Common Causes
- Short to ground in IAT sensor wiring
- Faulty IAT sensor
- Corroded sensor connector
- Failed PCM
How to Fix
- 1 Inspect wiring for shorts
- 2 Replace IAT sensor
- 3 Clean wiring harness connector
- 4 Test sensor with multimeter
Technical Explanation
The ECM detects code P0112 by continuously monitoring the relevant sensor circuit against calibrated threshold values stored in its non-volatile memory. The module measures the voltage return on the 5V reference circuit, comparing it to the expected signal envelope at current engine load and RPM. A deviation greater than the calibrated threshold — typically ±10% outside the normal operating window — flags the fault. The MIL illuminates after the fault is confirmed on two consecutive drive cycles, and the freeze frame data captured at first detection is stored in the PCM's memory for diagnostic reference.
Is It Safe to Drive?
Code P0112 allows for cautious short-distance driving, but the underlying cause — most likely short to ground in iat sensor wiring — will worsen with time. Fuel economy suffers, and ignoring the fault for weeks can turn a $50 fix into a much larger repair bill.
Mechanic's Pro Tip
Module replacement should always be the last resort for P0112 after exhaustively verifying all power supply circuits, ground connections, and communication bus wiring. Use a wiring diagram to locate all fuses, relays, and ground points for the affected module, and measure voltage drop on each ground with the circuit loaded. A module "failure" is frequently a corroded ground eyelet or a weak battery causing brownout conditions — fix these first and you'll save hundreds of dollars on an unnecessary module replacement.
IAT Sensor replacement: $80 - $200