P0112: Intake Air Temperature (IAT) Sensor 1 Circuit Low (Meaning, Causes, Fixes)
What P0112 means
The IAT sensor measures the temperature of the air going into the engine, and the engine computer (PCM) uses it to help set fuel delivery and, per RepairPal, ignition timing and some emission controls. OBD-Codes.com explains that the PCM supplies a 5-volt reference and a ground to the sensor, which is a thermistor: cold air gives high resistance and warmer air gives lower resistance, so a sensor or wire shorted to ground pulls the signal low and reads as very hot air. On many vehicles the IAT sensor is built into the mass air flow (MAF) sensor. Sources describe the trigger differently: OBD-Codes.com says the code sets when the PCM sees an unusually high intake air temperature (it gives 300 degrees as an example) while the engine is still relatively cool, while RepairPal says it sets when the IAT signal stays below 0.5 volts while coolant temperature readings are behaving normally. Thresholds vary by manufacturer. Related IAT codes include P0110 (circuit), P0111 (range/performance), P0113 (circuit high) and P0114 (intermittent).
Severity: can I keep driving?
Usually OK to drive
Usually OK to drive short-term, but get it diagnosed. RepairPal rates P0112 'Moderate' severity, and OBD-Codes.com says there may be no noticeable symptoms besides the check engine light. If the engine pings (knocks) under load, is hard to start, hesitates or runs poorly, get it checked sooner, and don't ignore new or flashing warning lights.
Common symptoms
- Check engine light on
- Often no other noticeable symptoms (per OBD-Codes.com)
- Engine pinging under load, or higher NOx readings on an emissions test, depending on how the sensor failed (per OBD-Codes.com)
- Hard starting or poor fuel economy in some cases (listed by RepairPal)
- Poor engine performance or hesitation on acceleration (listed by RepairPal)
Likely causes
Roughly most to least common, based on the sources below. Your vehicle may differ.
- Internally shorted, open or otherwise damaged IAT sensor (the usual cause, per OBD-Codes.com)
- Signal circuit shorted to ground
- Damaged, faulty or corroded IAT connector or wiring
- No reference voltage to the sensor because of an open wire (listed by OBD-Codes.com)
- Excessively high intake air temperatures (listed by OBD-Codes.com)
- Dirty air filter or a defective MAF sensor (listed by RepairPal)
- Faulty PCM (less likely)
Diagnostic steps you can do
Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.
- Read all stored codes. Other sensor or 5-volt supply codes appearing together can point to a shared wiring, ground or reference-voltage problem.
- Check the air filter and replace it if dirty.
- Find the IAT sensor (in the intake duct, air box, or built into the MAF sensor) and check its connector and wiring for damage, corrosion or chafing.
- With a scan tool showing live data on a cold engine, compare the IAT reading with the coolant temperature reading. OBD-Codes.com says they should roughly match, since both read ambient temperature after the car has sat.
- If the IAT reads far too hot, OBD-Codes.com says to unplug the sensor and recheck: the reading should drop to its minimum (around -20 degrees). If it does, the sensor is the likely fault; if it still reads high, the wiring or PCM needs testing (see below).
Typical fixes
- Replace the IAT sensor (or the MAF sensor where the IAT is built into it)
- Repair a signal wire shorted to ground, or other damaged IAT wiring
- Repair or replace a damaged IAT connector
- Replace a dirty air filter
- PCM repair or replacement only after the sensor and wiring are confirmed good
Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.
🛠 When to call a pro
- The reading stays too hot with the sensor unplugged. OBD-Codes.com describes a resistance check across the harness terminals to tell a shorted signal wire from a PCM fault.
- Testing needs a scan tool and a digital multimeter; RepairPal says to confirm a steady 5-volt reference and a good ground at the connector with the key on and engine off, using the correct wiring diagram
- The code comes back after a new sensor (owners on OBD-Codes.com forums report this on some Chrysler and Jeep models, which points to wiring)
- RepairPal warns the IAT sensor is often replaced when the real cause is a dirty air filter, a poor connection or chafed wiring, or the MAF sensor
Where to buy
Plain search links. Always match parts to your exact year, make, model and engine.
FAQs
Can I drive with P0112?
Usually yes for a short time. OBD-Codes.com says there may be no symptoms besides the check engine light, and RepairPal rates it 'Moderate'. Still get it diagnosed, because a false hot-air reading can affect fueling and timing, and OBD-Codes.com notes it can cause pinging under load or higher NOx on an emissions test.
Does P0112 mean the IAT sensor is bad?
Often, but not always. OBD-Codes.com says a bad sensor is the usual cause but lists a signal wire shorted to ground, a damaged connector and the PCM too, and RepairPal says the sensor is often replaced when the real cause is a dirty air filter, poor connection, chafed wiring or the MAF sensor.
What's the difference between P0112 and P0113?
P0112 is IAT circuit low (signal voltage too low, usually reported as very hot air), and P0113 is IAT circuit high (signal voltage too high, usually reported as very cold air).
Why does P0112 show up a lot on Nissan, Ford and Chevy searches?
Those makes show up often in searches for this code, but neither source names a model-specific problem. P0112 is a generic code, so diagnose it the same way, and check for service bulletins for your specific vehicle.
Sources
Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.