OBD-II trouble code
P0112: Intake Air Temperature Sensor Circuit Low Input
The IAT sensor signal voltage has dropped below the PCM's minimum threshold — which the computer reads as impossibly hot intake air. It's the mirror image of P0113: where that code means the circuit looks open, P0112 almost always means the signal is shorted to ground.
Quick facts
- System
- Powertrain
- Category
- Sensors / Air Intake
- Severity
- Low severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $80 – $400
- DIY difficulty
- Beginner DIY
What does P0112 mean?
P0112 sets when the voltage on the intake air temperature signal wire falls below the lowest value the PCM expects to see. To understand what that means, it helps to remember how the sensor works: the IAT is a thermistor whose resistance falls as air gets hotter. Low resistance pulls the signal voltage down, so when the PCM sees a very low voltage, it interprets that as extremely hot intake air — often a reading pinned near the top of the scale, something like 250-300°F that the engine couldn't actually be drawing in. That pinned-hot value is the diagnostic fingerprint of P0112.
This is the exact opposite end of the circuit from P0113. P0113 (high input) reads cold because the voltage is high, which usually points to an open circuit or a disconnected sensor. P0112 (low input) reads hot because the voltage is low, which almost always points to the signal wire shorting to ground somewhere — a chafed wire touching the block, a sensor that has internally shorted, or a connector flooded with moisture that's bridging the pins. Knowing which direction the reading is pinned tells you which failure family to chase before you ever pick up a multimeter.
The practical impact is mild. A pinned-hot IAT reading tells the PCM the air is thin and warm, so it tends to lean out the mixture and pull a little timing, which can show up as slightly weaker performance or a marginal economy change. The engine still runs on a default value once the PCM rejects the signal. As with the rest of the IAT family, the real reasons to fix it are the guaranteed emissions-test failure and the small efficiency penalty — not any risk of being left on the roadside.
Common causes
- Signal wire shorted to ground (chafed against the block, bracket, or intake)
- IAT sensor internally shorted
- Moisture or coolant bridging the connector pins
- Corrosion in the connector creating a low-resistance path
- Failing MAF/IAT combo unit on engines that share a housing
- Pinched harness after recent intake, air-box, or valve-cover work
- Aftermarket intake wiring routed against a sharp or hot edge
- Rodent damage shorting the signal and ground wires together
Symptoms
- Check engine light on with P0112 stored
- IAT live-data value pinned at the hot end of the scale (around 250-300°F)
- Slightly leaner-than-normal running on some engines
- Minor loss of power or throttle crispness
- Small fuel-economy change
- Emissions / smog test failure
Diagnostic steps
- 1.Read live data at key-on. An IAT value pinned at roughly 250-300°F on a cold engine is the classic low-input/short signature.
- 2.Unplug the IAT connector. If the live-data reading swings to the cold end (around -40°F) with the connector open, the sensor or the wiring downstream is shorting — the circuit itself can read high when truly open.
- 3.Inspect the connector for moisture, coolant, or green corrosion bridging the pins, and dry/clean it before retesting.
- 4.Measure resistance across the sensor terminals and compare to spec — a reading near zero confirms an internally shorted sensor.
- 5.If the sensor checks out, inspect the signal wire along its full run for chafe points against the block, brackets, or intake where it could short to ground.
- 6.On combo MAF/IAT housings, a confirmed internal short means replacing the assembly.
Repair cost
$80 – $400
A standalone IAT sensor that's shorted internally is the cheap fix — $20-$90 in parts and 0.4-1.5 hours of labor, roughly $80-$200 installed. A shorted signal wire is variable: a quick pigtail or splice repair can be under $100, but tracing and repairing a chafe buried in the harness can run higher. If the IAT is part of a mass airflow housing, the assembly runs $250-$400.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with intake air temperature sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is a beginner-friendly repair. Common hand tools, a free afternoon, and a willingness to follow a procedure are usually enough. The risk of causing a bigger problem is low if you read up on your specific vehicle first.