OBD-II Code P1111 — What It Means & How to Fix It

What Does This Error Mean?

P1111 means Intake Air Temperature Sensor has an Intermittent High reading. The Intake Air Temperature (IAT) sensor measures the temperature of air entering the engine. An intermittent high reading means the sensor occasionally spikes to an abnormally high voltage without a clear pattern. This is often a sign of a loose connector, a chafed wire, or a sensor that is starting to fail. You may not notice any drivability symptoms, or you may see very slight changes in fuel economy or throttle response.

Affected Models

Common in GM vehicles with IAT sensor monitoring on the PCM
Common in Chevrolet, Buick, Oldsmobile, and Pontiac vehicles from the late 1990s through 2010s
Also seen on some Ford and Chrysler vehicles with IAT circuits
Applies broadly to any vehicle with a standalone IAT sensor rather than one integrated in the MAF

Common Causes

Loose or corroded IAT sensor connector causing intermittent signal spikes
Chafed wire that intermittently shorts to a voltage source or opens the circuit
IAT sensor with a cracked or failing internal resistive element
Excessive engine heat soaking the sensor and causing spurious high readings
MAF/IAT combination sensor beginning to fail at the temperature sensing element

How to Fix It

Inspect the IAT sensor connector. Wiggle the connector while monitoring the sensor reading on a scan tool. An intermittent fault will spike the reading when the connector is disturbed.

An intermittent code that only appears during driving often points to a connector or wire that moves and causes a fault.
Check the sensor wiring for chafing against hot engine components. The IAT sensor is in the intake air path — wiring routed near the exhaust is at risk.

Repair any damaged insulation with heat-resistant wiring loom or replace the affected wire.
Test the IAT sensor resistance with a multimeter. The resistance should decrease as temperature increases. Compare readings to the specification table.

At room temperature (70°F/21°C), most IAT sensors read approximately 2,000 to 3,000 ohms. Higher or lower than spec indicates sensor failure.
Replace the IAT sensor if it fails the resistance test or if intermittent spikes cannot be resolved by connector or wiring repairs.

On many GM engines, the IAT sensor is a small probe mounted in the intake air duct and is easy to replace.
Clear the code and drive normally for several days. An intermittent code may not return immediately — monitor for recurrence.

If P1111 recurs, use freeze frame data to determine the conditions (engine temp, speed, rpm) when it sets.

When to Call a Professional

IAT sensor replacement costs $50 to $150. Wiring repair is $100 to $250. If integrated in the MAF sensor, replacement of the MAF/IAT assembly is $100 to $300. This is one of the more affordable sensor codes to diagnose and repair.

Frequently Asked Questions

Is P1111 serious?

Usually not. An intermittent IAT fault has minimal effect on drivability. The PCM uses substitute values when the sensor reading is out of range. Fix it when convenient — it is not urgent.

Can P1111 cause my check engine light to come on?

Yes — even intermittent faults that are detected a sufficient number of times will turn on the check engine light. The light may turn off on its own if the fault does not recur, but the code will remain stored.

Where exactly is the IAT sensor?

On most vehicles, the IAT sensor is located in the intake air duct between the air filter box and the throttle body. Some vehicles have the IAT integrated into the MAF sensor body. Your vehicle-specific repair manual shows the exact location.