Failing IAT sensor (OBD-Codes.com says it's usually the sensor unless the vehicle is very old). Poor connection at the IAT sensor or at the PCM. Open in the IAT signal or ground circuit, or a short to ground on the signal circuit. Corroded or chafed IAT wiring, more likely on older vehicles. Dirty air filter or a defective MAF sensor (listed by RepairPal).

Repair or clean the IAT sensor connector. Repair open, shorted, corroded or chafed IAT wiring. Replace the IAT sensor (or the MAF sensor where the IAT is built into it). Replace a dirty air filter.

P0111🔧 Air intake / intake air temperature sensorUsually OK to drive

P0111: Intake Air Temperature (IAT) Sensor 1 Circuit Range/Performance (Meaning, Causes, Fixes)

Q: What does P0111 mean?

P0111 means the engine computer thinks the intake air temperature (IAT) sensor signal is not behaving believably: it jumps too much too fast, or doesn't agree with the coolant temperature reading. The usual causes are a failing IAT sensor or a poor connection or wiring fault in its circuit. 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 sensor is a thermistor fed 5 volts by the PCM: cold air means high resistance and a high signal voltage, warm air means low resistance and a low signal voltage. Unlike P0112 (circuit low) and P0113 (circuit high), P0111 is a 'range/performance' code, and the two sources describe its trigger a little differently. OBD-Codes.com says it sets when the PCM sees a larger-than-normal change in the IAT signal in a shorter-than-expected time, which usually points to an intermittent fault. RepairPal says it sets when the signal is erratic or goes outside the expected range compared with the engine coolant temperature (ECT) sensor reading. The exact test varies by manufacturer. On many vehicles the IAT sensor is built into the mass air flow (MAF) sensor. Related IAT codes include P0110 (circuit), P0112 (circuit low), P0113 (circuit high) and P0114 (intermittent).

Q: Can I keep driving with P0111?

Usually OK to drive. Usually OK to drive short-term, but get it diagnosed. RepairPal rates P0111 'Moderate' severity, and OBD-Codes.com says there will most likely be no noticeable symptoms other than the check engine light. If the engine is hard to start, hesitates on acceleration or runs poorly, get it checked sooner, and don't ignore new or flashing warning lights.

Reviewed 2026-10-24 · Based on 2 cited source(s)

What P0111 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 sensor is a thermistor fed 5 volts by the PCM: cold air means high resistance and a high signal voltage, warm air means low resistance and a low signal voltage. Unlike P0112 (circuit low) and P0113 (circuit high), P0111 is a 'range/performance' code, and the two sources describe its trigger a little differently. OBD-Codes.com says it sets when the PCM sees a larger-than-normal change in the IAT signal in a shorter-than-expected time, which usually points to an intermittent fault. RepairPal says it sets when the signal is erratic or goes outside the expected range compared with the engine coolant temperature (ECT) sensor reading. The exact test varies by manufacturer. On many vehicles the IAT sensor is built into the mass air flow (MAF) sensor. Related IAT codes include P0110 (circuit), P0112 (circuit low), 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 P0111 'Moderate' severity, and OBD-Codes.com says there will most likely be no noticeable symptoms other than the check engine light. If the engine is hard to start, hesitates on acceleration 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, since the fault is usually intermittent (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.

Failing IAT sensor (OBD-Codes.com says it's usually the sensor unless the vehicle is very old)
Poor connection at the IAT sensor or at the PCM
Open in the IAT signal or ground circuit, or a short to ground on the signal circuit
Corroded or chafed IAT wiring, more likely on older vehicles
Dirty air filter or a defective MAF sensor (listed by RepairPal)

Diagnostic steps you can do

⚠ Before you start

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. OBD-Codes.com says to diagnose any other IAT codes (such as P0110, P0112 or P0113) first.
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 that its connector is fully seated, clean and not corroded.
On a cold engine that has sat for hours, compare the IAT and coolant temperature readings on a scan tool with the key on and engine off. OBD-Codes.com says they should read about the same; if they do, the problem is likely intermittent.
If your scan tool shows freeze frame data, look at the IAT reading when the code set. OBD-Codes.com says a reading near -30 F points to an intermittent open or high resistance, and a reading above about 250 F points to an intermittent short to ground.
With the engine running, gently wiggle the IAT wiring and connector while watching the live IAT reading for sudden jumps.

Typical fixes

Repair or clean the IAT sensor connector
Repair open, shorted, corroded or chafed IAT wiring
Replace the IAT sensor (or the MAF sensor where the IAT is built into it)
Replace a dirty air filter

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 code comes back after checking the connector and wiring
Testing needs a scan tool and a multimeter: checking for a steady 5-volt reference and good ground at the connector (per RepairPal), and watching the sensor's resistance change smoothly as it's cooled and warmed (per OBD-Codes.com)
The fault can't be reproduced in the driveway and needs a road test while logging IAT against coolant temperature, load, RPM and speed
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.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0111?

Usually yes for a short time. OBD-Codes.com says there are most likely no noticeable symptoms, and RepairPal rates it 'Moderate'. Still get it diagnosed, because a bad IAT reading can affect fueling, starting and fuel economy.

What's the difference between P0111 and P0112 or P0113?

P0112 and P0113 mean the IAT signal voltage is stuck too low or too high. P0111 means the signal is within the possible range but isn't believable: it changes too quickly (per OBD-Codes.com) or doesn't agree with the coolant temperature reading (per RepairPal).

Does P0111 mean the IAT sensor is bad?

Often, but not always. OBD-Codes.com says it's usually the sensor unless the vehicle is very old and the harness is worn, while RepairPal warns the sensor is often replaced when the real cause is a dirty air filter, a poor connection, chafed wiring or the MAF sensor.

Can P0111 show up after an air filter change?

It can if the IAT or MAF connector was knocked loose or not reconnected properly. Check the connector first.

Sources

Last reviewed 2026-10-24. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.