P0112 means the intake air temperature (IAT) sensor’s signal voltage is lower than expected, which the computer reads as extremely hot intake air. It is the opposite of P0113 (signal high, reading very cold). The IAT sensor is a minor input, so symptoms are usually mild, but the cause is often a simple sensor or wiring fault worth fixing.
What Does P0112 Mean?
The IAT sensor is a thermistor — a small resistor whose resistance changes with temperature. The computer sends it a reference voltage and reads what comes back. On most designs, a hot sensor has low resistance and a low return voltage. P0112 is stored when that voltage is so low that the reading implies an air temperature that cannot realistically be correct. The computer uses intake air temperature to fine-tune fuel and timing, so a wrong value can nudge both.
The mirror-image fault is P0113, where the voltage is too high and the reading says the air is extremely cold. On many cars the IAT sensor is built into the MAF sensor, so the code can point to that part — see P0102 for MAF faults.
With the engine cold, a scan tool should show an intake air temperature close to the outside temperature. If it shows an extreme value, unplug the sensor: the reading should swing to the opposite extreme, typically around minus 40 degrees. If it does not, the wiring is shorted to ground.
Common Symptoms
- Check engine light on, often with no other obvious sign — see check engine light on but car runs fine.
- Slightly rough running when cold — see engine runs rough only when cold.
- Mild hesitation or lower fuel economy in some cars.
- Harder cold starting in some cases — see car won’t start in cold weather only.
Common Causes, Most Likely First
- A failed IAT sensor with internal resistance too low.
- A signal wire shorted to ground through damaged insulation.
- A damaged or corroded connector.
- A failed MAF sensor on cars where the IAT sensor is built into it.
- A rare computer fault, once everything else is cleared.
How to Diagnose It
- Read live IAT data with the engine cold. Compare it with the outside temperature.
- Unplug the sensor and see whether the reading swings to the opposite extreme.
- Inspect the connector and wiring for chafing, corrosion or moisture.
- Check whether the sensor is part of the MAF sensor on your car.
- Replace the sensor if the wiring tests good. See our OBD-II scanner guide and how to reset a check engine light once the repair is done.
Let the engine and exhaust cool before touching sensors, connectors or hoses, and never open a hot cooling system. Keep hands and loose clothing away from belts and fans, which can start on their own.
Possible Fixes
| Cause | Fix | Typical cost |
|---|---|---|
| Failed standalone IAT sensor | Replace the sensor | $15 – $120 |
| Shorted wiring | Repair the harness | $50 – $250 |
| Corroded connector | Clean or replace the connector | $20 – $150 |
| IAT built into MAF sensor | Replace the MAF sensor | $120 – $450 |
Can I Drive With P0112?
Usually yes — the IAT sensor is a secondary input and many cars run almost normally with it faulted. Fix it reasonably soon, though, because the wrong temperature can slightly skew fuelling, and a standing fault can mask other problems; if the light begins to flash, follow our flashing light guide.
When to See a Mechanic
If replacing the sensor does not clear the code, or you cannot find the wiring fault. More in our engine section.
Frequently Asked Questions
What does P0112 mean?
The intake air temperature sensor’s circuit voltage is too low, which the computer reads as extremely hot intake air.
What is the difference between P0112 and P0113?
P0112 is a low-voltage signal that reads extremely hot; P0113 is a high-voltage signal that reads extremely cold.
Is the IAT sensor part of the MAF sensor?
On many cars, yes. Check your vehicle, because it decides whether you replace a small sensor or the whole MAF assembly.
Can I drive with P0112?
Usually yes, as the IAT sensor is a secondary input, but you should fix it reasonably soon.
How much does it cost to fix P0112?
A standalone sensor is often $15–$120; wiring repairs or a MAF replacement cost more.
