Fuel and air

P0111 — Intake Air Temperature Sensor Circuit Range/Performance

Severity: low Safe to drive

What P0111 means

The engine control unit monitors the intake air temperature (IAT) sensor and compares its reading with other data such as coolant temperature, ambient temperature and engine warm-up. If the signal does not make sense, jumps around or stays stuck, the ECU sets P0111. Air temperature is used to calculate air density, which affects fuel delivery and ignition timing.

Symptoms

  • Check Engine light on
  • Reduced fuel economy
  • Rough idle
  • Hesitation or stumbling on acceleration
  • Hard starting, especially cold or hot
  • Slightly reduced power

Possible causes

  1. Failed intake air temperature (IAT) sensor
  2. Damaged, corroded or chafed wiring or connector at the sensor
  3. Open or short in the signal wire or sensor ground
  4. Sensor contaminated with oil or dirt, or mounted in a hot spot
  5. Air intake leaks, or a faulty MAF sensor when the IAT is built into it
  6. Rarely, an ECU hardware or software fault

How to diagnose

  1. Scan for codes and review freeze frame data; look for related MAF, coolant temperature or MAP codes
  2. On a cold engine (after sitting overnight), compare IAT with coolant and ambient temperature; they should be close
  3. Inspect the sensor connector and harness for corrosion, moisture, chafing and loose pins
  4. Measure sensor resistance with a multimeter and compare it to the spec for your vehicle at the known temperature
  5. Check the reference voltage (usually about 5 V) and ground at the connector
  6. Watch live data while the engine warms up; the reading should rise smoothly, not jump
  7. Inspect the air filter and intake tract for restrictions and leaks
  8. If the IAT is built into the MAF sensor, test or replace the MAF assembly

Common fixes

  • Replace the IAT sensor, or the MAF assembly if the IAT is integrated
  • Repair damaged wiring and clean or replace the connector
  • Replace a clogged air filter and fix intake leaks
  • Clean the sensor with a suitable cleaner if it is dirty
  • Repair or reprogram the ECU in rare cases

Questions and answers

Can I drive with a P0111 code?

Usually yes, because the ECU uses an estimated value. But expect worse fuel economy, a rough idle and possible hesitation, so have it diagnosed soon.

What most often causes P0111?

Most often it's the IAT sensor itself or a poor connection in its connector or wiring. Check the wiring and connector first, then test the sensor.

Can I just clear the P0111 code?

You can, but if the cause isn't fixed the code will come back. Check the sensor readings and circuit first to find the real fault.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.