# P0112: Intake Air Temperature Sensor 1 Circuit Low (Bank 1) **Verdict:** Safe to drive Air intake - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $50-$450 - **Urgency:** Keep driving - **Most likely:** Shorted IAT sensor or wiring - **DIY?:** Yes, steps 1-4 ## Quick answer P0112 means the signal from the intake air temperature (IAT) sensor is reading too low on voltage, which the computer sees as extremely hot air. That usually points to a shorted sensor or a signal wire touching ground. The car normally runs close to normal, but the code should still be fixed. ## What does P0112 mean? The IAT sensor is a thermistor that measures the temperature of air entering the engine. Its resistance falls as the air warms. The engine computer supplies a reference voltage, usually 5 volts, and reads what is left on the signal wire: high voltage for cold air, low voltage for hot air. It uses the reading to fine-tune fuel delivery and ignition timing, and on some engines to cross-check the coolant sensor after the car has sat overnight. P0112 sets when the signal voltage drops near zero, which a scan tool usually shows as an impossibly hot reading, often well above 250 degrees F. Real intake air never gets that hot, so the computer assumes a short to ground or a failed sensor. Many makers set it within seconds on one or two trips and use a default temperature. "Sensor 1" is the main IAT, which on many cars is built into the MAF sensor. ## What are the symptoms of P0112? - Check engine light on - Car usually runs normally - Possible harder starting when the engine is cold - Slightly reduced power on some engines, which pull spark timing for hot air - Slightly worse fuel economy ## What causes P0112? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Internally shorted IAT sensor** (most common). Thermistors can develop internal shorts after years of heat cycling and vibration, especially sensors mounted near hot engine parts or exposed to oil vapor. A shorted sensor drives the signal near zero. With the connector unplugged, the reading should jump to about -40 degrees; if it does, the wiring is fine and the sensor is bad. 2. **Signal wire shorted to ground** (common). If the insulation on the signal wire wears through and touches the engine, a bracket or a ground wire, the voltage is pulled low. Look where the harness bends at the air box, passes under clamps or sits near hot surfaces. Rodent damage and wires crushed during earlier repairs are other common places to find bare copper. 3. **Failed MAF sensor with built-in IAT** (common). Many vehicles house the IAT inside the MAF sensor and share one connector. A short in that internal element sets P0112 even though airflow readings stay normal. The IAT part cannot be replaced separately in these designs, so the fix is a complete MAF sensor, which costs several times more than a standalone IAT sensor. 4. **Moisture or corrosion in the connector** (less common). Water or corrosion in the IAT or MAF connector can create a low-resistance path between the signal and ground pins. It often follows engine washing, a blocked cowl drain or driving through deep water, and the code may come and go with the weather. Clean, dry and inspect the terminals, and replace the connector if pins are green or loose. 5. **Engine computer input fault** (rare). An internal short on the computer's IAT input is uncommon. It is considered only after the code stays with the sensor unplugged and the signal wire tests good from end to end. A shop also checks whether other sensors sharing the same sensor ground show odd readings, which can point to a computer-side problem. ## How do you diagnose P0112? 1. Read IAT on a scan tool after the car has sat overnight; it should match outside temperature within a few degrees. 2. Unplug the IAT or MAF connector; the reading should jump to about -40 degrees if the wiring is good. 3. If the reading stays hot with the sensor unplugged, look for a signal wire shorted to ground. 4. Check the connector for water and corrosion, and measure sensor resistance against the maker's temperature chart. ## How do you fix P0112, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Replace standalone IAT sensor | $50-$200 | Often twists or clips into the air intake tube or air box. | | Replace MAF sensor with built-in IAT | $150-$450 | Needed when the IAT element is part of the MAF assembly. | | Repair wiring or connector | $100-$400 | For chafed wires, rodent damage or corroded terminals. | Full price breakdowns: [mass air flow sensor replacement cost](/cost/mass-air-flow-sensor-replacement). ## Is it safe to drive with P0112? > **Safe to drive.** Yes, it is generally safe to drive with P0112 for a while, since the computer substitutes a default air temperature. Fix it within a few weeks to protect fuel economy and pass inspection, and sooner if starting or running gets noticeably worse. ## Will P0112 fail an emissions test? P0112 turns on the check engine light, so the car will fail an OBD-II emissions test in most states even if it runs fine. The IAT reading also feeds fuel control, so emissions can rise slightly. After the repair, clear the code and drive normally for several days so the readiness monitors can complete before testing. ## After the repair: clearing P0112 After fixing it, clear the code and check IAT on a scan tool. On a cold engine it should match outside air temperature, and while driving it should stay in a believable range, typically a little warmer than outside air at idle and closer to it at speed. If no pending code returns over a few days, the fix worked. ## How to prevent P0112 - Seat the air box lid and MAF connector carefully after every air filter change. - Avoid over-oiling reusable air filters, since oil can coat the MAF and IAT sensor. - Keep harness clips in place so the IAT wiring cannot rub on metal edges. - Clear leaves from the cowl drains so water does not reach engine bay connectors. ## Codes often seen with P0112 - [P0113](/codes/p0113): Intake Air Temperature Sensor 1 Circuit High (Bank 1) - [P0101](/codes/p0101): Mass or Volume Air Flow "A" Circuit Range/Performance - [P0102](/codes/p0102): Mass or Volume Air Flow "A" Circuit Low - [P0117](/codes/p0117): Engine Coolant Temperature Sensor 1 Circuit Low - [P0171](/codes/p0171): System Too Lean (Bank 1) ## Frequently asked questions ### Can I drive with a P0112 code? Yes, you can usually drive with P0112, because the engine computer switches to a default air temperature and the car runs close to normal. You may notice slightly worse fuel economy or harder cold starts. Fix it within a few weeks, since the check engine light will hide any new problems. ### What does IAT sensor circuit low mean? Circuit low means the voltage from the intake air temperature sensor is close to zero. Because the sensor's voltage falls as air gets hotter, the computer reads that as impossibly hot intake air. It concludes the sensor is shorted or the signal wire is touching ground, and sets P0112. ### What causes P0112? A shorted intake air temperature sensor is the most common cause of P0112. A signal wire rubbed through to ground and a failed MAF sensor with a built-in IAT element are also common. Water or corrosion in the connector, and rarely an engine computer fault, can also set the code. ### How much does it cost to fix P0112? Most P0112 repairs cost $50 to $450 at an independent shop. A standalone IAT sensor runs $50 to $200. If the IAT is built into the MAF sensor, the whole MAF assembly is replaced for about $150 to $450. Wiring and connector repairs cost $100 to $400. ### What is the difference between P0112 and P0113? P0112 means the IAT signal voltage is too low, which reads as very hot air and usually points to a short. P0113 means the voltage is too high, which reads as very cold air and usually points to an open circuit, such as an unplugged connector or a broken wire. ### Can I fix P0112 myself? Yes, P0112 is often a reasonable home repair. Many IAT sensors twist or clip into the intake tube, and MAF sensors usually come out with two screws. A scan tool helps confirm the fix. Check the wiring for chafing first, because a new sensor will not fix a shorted wire. ### Where is the IAT sensor located? The IAT sensor is usually in the air intake tube, in the air filter box or built into the MAF sensor just after the air filter. Some engines also have a second air temperature sensor in the intake manifold. Service information for your engine shows which one is "sensor 1". ### Can a bad IAT sensor cause poor gas mileage? Yes, a bad IAT sensor can lower gas mileage a little. When the reading is wrong, or the computer falls back to a default value, fuel and timing are less well matched to real conditions. The change is usually small, so a big drop in mileage suggests another problem as well. ### Can I test an IAT sensor with a multimeter? Yes, you can test an IAT sensor by measuring its resistance at a known temperature and comparing it with the maker's chart. Resistance should drop as the sensor warms. A reading near zero ohms means a short, which matches P0112. MAF-mounted versions may need the maker's pin chart. ### Will a P0112 code clear itself? A P0112 code may clear itself if the short is intermittent, such as moisture that dries out, and the circuit passes on several trips. The computer keeps the code in history, though. If P0112 keeps coming back, inspect the wiring and connector, since an intermittent short tends to get worse. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) - [EPA: On-Board Diagnostics (OBD)](https://www.epa.gov/state-and-local-transportation/vehicle-emissions-board-diagnostics-obd) ## Other air intake codes - [P0101 Mass or Volume Air Flow "A" Circuit Range/Performance](https://diagxcar.com/codes/p0101) - [P0102 Mass or Volume Air Flow "A" Circuit Low](https://diagxcar.com/codes/p0102) - [P0106 Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance](https://diagxcar.com/codes/p0106) - [P0107 Manifold Absolute Pressure/Barometric Pressure Circuit Low](https://diagxcar.com/codes/p0107) - [P0108 Manifold Absolute Pressure/Barometric Pressure Circuit High](https://diagxcar.com/codes/p0108) - [P0113 Intake Air Temperature Sensor 1 Circuit High (Bank 1)](https://diagxcar.com/codes/p0113) - [P0117 Engine Coolant Temperature Sensor 1 Circuit Low](https://diagxcar.com/codes/p0117) - [P0118 Engine Coolant Temperature Sensor 1 Circuit High](https://diagxcar.com/codes/p0118) - [P0121 Throttle/Pedal Position Sensor/Switch "A" Circuit Range/Performance](https://diagxcar.com/codes/p0121) - [P0122 Throttle/Pedal Position Sensor/Switch "A" Circuit Low](https://diagxcar.com/codes/p0122) ## Symptoms - [Why is my car getting bad gas mileage?](https://diagxcar.com/symptoms/poor-gas-mileage) - [Why does my car hesitate when I accelerate?](https://diagxcar.com/symptoms/car-hesitates-when-accelerating) ## Repair costs - [Mass air flow sensor replacement cost](https://diagxcar.com/cost/mass-air-flow-sensor-replacement): $150-$450 --- Source page: https://diagxcar.com/codes/p0112 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.