AutoDiag

P0111

Intake Air Temperature Sensor 1 Circuit Range/Performance (Bank 1)

Low· Fix when convenientDIY friendlyPowertrainGeneric, all makes

What it means

The intake air temperature (IAT) sensor is sending a signal that is electrically valid but does not make sense compared with other sensors. The intake air temperature (IAT) sensor measures the temperature of the air entering the engine, which the ECU uses to fine-tune fuel and ignition timing. This usually points to a sensor that is reading wrong, or to a real mechanical problem it is reporting correctly, rather than a broken wire.

Is it safe to drive?

Safe to drive. The ECU uses a default value, so you may notice slightly worse economy or cold starts.

Symptoms

  • Check engine light on
  • Slight hesitation or rough running
  • Hard starting in cold weather
  • Reduced fuel economy

Probable causes

Most likely first

  1. 1Sensor reading stuck and not matching coolant temperature after a cold soak
  2. 2Sensor mounted in a hot location or heat-soaked
  3. 3Failing sensor giving an inaccurate reading
  4. 4Poor connection at the sensor connector

How to diagnose it

Work through these in order before buying parts

  1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
  2. 2Inspect the intake air temperature (IAT) sensor connector and wiring (in the air filter box, intake tube or built into the MAF sensor). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
  3. 3Watch the intake air temperature (IAT) sensor reading on live data. After the car has sat overnight, IAT and coolant temperature should read within a few degrees of each other and of the outside temperature.
  4. 4Compare the intake air temperature (IAT) sensor reading against related sensors and the real-world condition. If they disagree, find out which one is telling the truth before buying parts.
  5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
  6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

  • Fix the underlying problem the sensor is reporting, if real
  • Replace the intake air temperature (IAT) sensor if it reads wrong against a known-good reference

This information is general guidance for all makes. Exact causes, specifications and procedures vary by vehicle, so confirm with your service manual or a qualified mechanic before replacing parts.