OBD Code P0112: Intake Air Temperature Circuit Low Input

Q: What does OBD code P0112 mean?

Intake Air Temperature Circuit Low Input. The engine computer detected that the intake air temperature sensor is reading colder than physically possible, like a thermometer stuck at freezing on a hot day. This tells the ECU something is wrong with the sensor circuit or its wiring.

Q: What are the symptoms of fault code P0112?

Check Engine Light illuminated, Rich fuel mixture (black smoke from exhaust), Poor fuel economy and sluggish acceleration

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What This Actually Means

In plain language — no jargon

The engine computer detected that the intake air temperature sensor is reading colder than physically possible, like a thermometer stuck at freezing on a hot day. This tells the ECU something is wrong with the sensor circuit or its wiring.

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Symptoms You May Notice

3 known symptoms for this code

Check Engine Light illuminated

Rich fuel mixture (black smoke from exhaust)

Poor fuel economy and sluggish acceleration

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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECM monitors voltage from the Intake Air Temperature (IAT) sensor, which is a thermistor that changes resistance based on air temperature. The sensor normally reads between -40°F and 250°F; a low input fault occurs when the voltage signal falls below the minimum acceptable threshold, indicating either a shorted sensor, damaged wiring, or connector issue.

Voltage & Parameter Thresholds

Parameter	Normal Range	Fault Condition
IAT Sensor Voltage	0.5V to 4.5V (representing -40°F to +250°F)	Below 0.1V or stuck at minimum value
Air Temperature Reading	-40°F to +250°F	Below -50°F or implausibly cold

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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

IAT sensor connector

Inspect and reseat the connector at the intake air temperature sensor for corrosion or loose pins.

2

Wiring harness (IAT circuit)

Check the sensor wiring for breaks, shorts, or damage between the sensor and ECM.

3

Intake Air Temperature sensor

Replace the sensor if voltage readings are erratic or stuck low after connector and wiring checks.

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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code P0112 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.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.

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How to Clear Code P0112

What happens after you fix the fault

Once the fault is repaired, P0112 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.

✅ Safe to Clear When

Fault has been diagnosed and repaired
You want to confirm the repair worked
Code appeared after a sensor was cleaned

⚠️ Do Not Clear When

Preparing for an emissions/PUC test
Root cause is still undiagnosed
Check engine light is flashing

Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.