P0112 Code: Low Input in IAT Sensor Circuit
P0112 IAT Sensor Circuit Low Input Causes & Fixes. See symptoms, common causes, driving risk and checks that help confirm the fault before parts are replaced.
Save all codes and freeze-frame data. The code tells you what the control module detected, not which component must be replaced.
Quick answer
OBD2 code P0112 indicates the engine control module (ECM) has detected an abnormally low voltage signal from the Intake Air Temperature (IAT) sensor circuit. In most cases, this means the sensor or its wiring is reporting a temperature far below the expected range, often signaling an open circuit, short to ground, or a failed sensor.
What the P0112 Code Means: IAT Circuit Low Input Explained
The Intake Air Temperature (IAT) sensor measures the temperature of the air entering the engine and sends this data to the ECM as a voltage signal. The ECM uses this input to adjust fuel delivery and ignition timing for optimal performance and emissions. Under normal conditions, the IAT sensor's resistance changes with temperature: colder air increases resistance (higher voltage), while warmer air lowers resistance (lower voltage).
When the P0112 code sets, the ECM detects a voltage reading that is too low for the current conditions. This typically occurs when the sensor's circuit is open (no signal) or shorted to ground, causing the voltage to drop below the expected minimum threshold; often near 0 volts. The ECM interprets this as an impossibly cold temperature (e.g., -40°F or lower), which is unrealistic under normal operating conditions, so it triggers the code and may illuminate the check engine light.
Common scenarios that trigger P0112 include a disconnected or damaged sensor, corroded or broken wiring in the sensor's circuit, or an internal fault within the IAT sensor itself. In some vehicles, the IAT sensor is integrated into the mass airflow (MAF) sensor assembly, so issues with the MAF sensor can also produce a false IAT reading. The ECM may also detect this low input if the 5-volt reference wire or ground wire to the IAT sensor is faulty, as these are critical for accurate signal transmission.
It's worth noting that the IAT sensor is often located in the intake manifold or air intake hose, where it's exposed to heat and vibrations. Over time, the sensor's electrical connections can degrade, or the sensor itself may fail due to age or contamination. In rare cases, a faulty ECM could misinterpret the signal, but this is far less common than sensor or wiring issues.
Diagnosing P0112 requires checking the IAT sensor's resistance and voltage output with a multimeter, inspecting the wiring harness for damage or corrosion, and verifying the integrity of the 5-volt reference and ground circuits. If the sensor is within specification but the code persists, the issue may lie in the wiring or connectors between the sensor and the ECM.
Symptoms of P0112
Drivers often notice poor engine performance, such as rough idling or hesitation during acceleration, as the ECM struggles to compensate for the incorrect temperature data. In some cases, the engine may run rich (excess fuel) or lean (insufficient fuel), leading to reduced fuel efficiency. The check engine light will typically be illuminated, and in severe cases, the vehicle may enter a limp mode to prevent damage.
Common Causes of P0112
The most frequent causes include a faulty IAT sensor, damaged or corroded wiring in the sensor circuit, or a poor electrical connection at the sensor or ECM. Less commonly, a failed MAF sensor (if the IAT is integrated) or a short to ground in the signal wire can trigger the code. Repairs typically range from $150 to $400 depending on the cause ; see the full P0112 repair cost guide for a detailed breakdown.
Can You Still Drive With Code P0112?
In most cases, you can continue driving with P0112, but it's not advisable for long. The ECM will use default values for intake air temperature, which can lead to poor fuel economy, reduced performance, or even engine damage over time. If the vehicle is running rough or overheating, pull over and have it towed to avoid further issues.
Related Codes
P0113 is the companion code for a high input signal from the IAT circuit, often caused by a short to voltage. P0101 may appear if the MAF sensor (with integrated IAT) is faulty, as it monitors airflow and temperature together. P0125 can also be related, as the ECM may struggle to balance fuel delivery without accurate temperature data.
Details that improve the diagnosis
Compare the reported value with engine temperature, barometric pressure, throttle position and related sensors. A signal that is electrically valid can still be implausible. Fuel trims at idle and at a steady higher speed help separate an intake leak from a fuel-delivery or measurement problem.
Before clearing anything, record whether the code is current, pending, history or permanent. Save companion codes and freeze-frame conditions, then note recent repairs, a weak battery, weather changes and the exact moment the symptom appears. After a confirmed repair, clear only the erasable codes and complete the appropriate drive cycle. A permanent code normally clears only after the onboard monitor verifies that the fault is gone.
Related trouble codes
Information to record before any repair
Write down the exact code, its status and every companion code reported by a complete vehicle scan. Save the freeze-frame values, including engine speed, load, coolant temperature, vehicle speed, battery voltage and fuel trims when available. Note whether the warning appeared during a cold start, at idle, under acceleration, after refueling, in wet weather or immediately after other work. These details help separate an intermittent electrical problem from a repeatable mechanical or operating-condition fault.
Identify the exact year, make, model, engine, transmission and market version before using a wiring diagram or specification. Connector pinouts, monitor thresholds, component locations and test procedures can change within the same model line. Check current manufacturer service information and relevant technical service bulletins. A bulletin can improve the test sequence, but it should not be treated as proof that the same fault exists on every vehicle.
How to verify the repair
A warning light that stays off immediately after codes are cleared does not by itself confirm a repair. Recheck live data, repeat the operating condition that originally set the code when it is safe to do so, and confirm that no pending code returns. Some monitors need a specific drive cycle before they run. Permanent codes are normally removed by the control module only after it sees enough successful monitor results. If symptoms remain or the code returns, continue testing instead of replacing another part by guesswork.