Fuel and air

P0112 — Intake Air Temperature Sensor Circuit Low Input

Severity: low Safe to drive

What P0112 means

The engine control module sends a 5 V reference to the intake air temperature (IAT) sensor and reads the voltage drop to work out air temperature. The sensor's resistance falls as air heats up, so the signal voltage drops too. P0112 sets when that voltage is lower than expected, as if the air were extremely hot. The cause is usually the sensor itself or a signal wire shorted to ground.

Symptoms

  • Check Engine light on
  • Hard starting when the engine is cold
  • Rough idle, especially when cold
  • Poor fuel economy
  • Hesitation or sluggish throttle response
  • Occasional stalling

Possible causes

  1. Failed IAT sensor (including one built into the MAF sensor)
  2. Corroded or damaged sensor connector
  3. Signal wire shorted to ground from worn insulation
  4. Open or poor ground wire for the sensor
  5. Faulty ECM (rare)

How to diagnose

  1. Read the codes and live data, and compare IAT with the actual ambient temperature on a cold engine
  2. If IAT reads extremely high (around 250°F / 120°C or more) on a cold engine, that confirms the low signal
  3. Inspect the sensor connector and harness for corrosion, chafing, heat damage or moisture
  4. Unplug the sensor: if the IAT reading jumps to its minimum (about −40°), the sensor is bad and the circuit is fine
  5. Measure the sensor's resistance and compare it with the spec at a known temperature
  6. Check for about 5 V reference at the connector with the sensor unplugged
  7. Test the signal wire for a short to ground and check the ground wire continuity
  8. If the sensor and wiring pass, test the ECM

Common fixes

  • Replace the IAT sensor, or the MAF sensor if the IAT is part of it
  • Clean or replace a corroded connector
  • Repair or replace the damaged section of wiring
  • Diagnose and repair or replace the ECM as a last resort

Questions and answers

What does P0112 mean?

The ECM is getting too low a voltage from the intake air temperature sensor, as if the air were very hot. It is most often a bad sensor or a signal wire shorted to ground.

Can I drive with a P0112 code?

Usually yes, but the engine may start poorly when cold, idle roughly and use more fuel. It's best to fix it soon.

How do I tell a bad sensor from a wiring problem?

Unplug the sensor and watch the IAT reading. If it drops to the minimum, the circuit is fine and the sensor is bad. If it stays high, look for a short to ground in the wiring.

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.