Fuel and air

P0127 — Intake Air Temperature Too High

Severity: low Safe to drive

What P0127 means

The intake air temperature (IAT) sensor tells the engine computer how hot the air entering the engine is. The ECM uses this to adjust fueling and ignition timing. P0127 sets when the signal reads above the expected limit, either because the air really is too hot or because the sensor or its circuit is faulty.

Symptoms

  • Check engine light on
  • Reduced power and sluggish acceleration
  • Worse fuel economy
  • Rough idle
  • Hesitation when accelerating
  • Abnormal fuel trims

Possible causes

  1. Failed IAT sensor
  2. Damaged wiring or corroded connector at the sensor
  3. Signal wire shorted to ground
  4. Faulty MAF sensor with built-in IAT
  5. Genuinely hot intake air from heat soak or intake routing problems
  6. Rarely, an ECM fault

How to diagnose

  1. Scan for codes and freeze frame data, and note any MAF or other IAT codes
  2. On a cold engine, compare IAT reading with ambient and coolant temperature
  3. Inspect the sensor connector and harness for corrosion, chafing, or heat damage
  4. Measure sensor resistance and compare to the manufacturer's temperature chart
  5. Unplug the sensor: the reading should drop to cold; if it still reads hot, look for a short to ground in the harness
  6. Check reference voltage and ground at the connector with a multimeter
  7. Inspect the intake path for hot air being drawn in, such as damaged ducting near the exhaust manifold
  8. Check the MAF sensor condition if the IAT is built into it

Common fixes

  • Replace the IAT sensor
  • Repair or replace damaged wiring and connectors
  • Clean or replace the MAF sensor if it contains the IAT
  • Restore proper cool-air intake routing
  • Rarely, update software or replace the ECM

Questions and answers

What does P0127 mean?

The ECM is getting a signal from the intake air temperature sensor that corresponds to a very high temperature. It is most often a sensor or wiring problem, and less often truly overheated intake air.

Can I drive with code P0127?

Usually yes for a short time. You may see lower power and worse mileage, so have it checked soon.

How do I test an IAT sensor?

Compare its reading on a cold engine to the outside air temperature, and measure its resistance against the manufacturer's chart. If unplugging it doesn't change the reading, suspect a wiring short.

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.