P0112Generic code

P0112 Code: Intake Air Temperature Sensor Circuit Low

The P0112 code means the IAT sensor signal is below its minimum value. On a thermistor, that means the computer reads an impossibly high temperature, almost always because of a short to ground.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$15 to $150
Difficulty
Easy
System
Air and Fuel
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0112 code means

The intake air temperature (IAT) sensor sits in the air filter box, in the intake duct, or built into the MAF sensor. The computer relies on it because it adjusts the amount of fuel and the spark advance according to air density.

The sensor is an NTC thermistor: its resistance drops as the temperature rises. The computer sends it 5 V and reads the resulting voltage. A signal below the minimum (normally less than 0.1 to 0.2 V) is the same as an impossibly high temperature, and that almost always means a short to ground: the signal wire touches metal, or the sensor is shorted inside. While the fault lasts, the computer believes the air is very hot, leans out the mixture slightly and retards the spark, which means less power and sometimes hard starting when cold.

Remember that the P0112 code points to the circuit where the computer saw the anomaly, not necessarily the failed part. Check the wiring before you replace the sensor, and test the IAT sensor step by step as described below.

P0112 code symptoms

  • Check engine light on steadily.
  • The computer believes the air is very hot, leans out the mixture slightly and retards the spark: less power and sometimes hard starting when cold.
  • In many cases you notice nothing while driving, just the light on the dash.
  • Companion codes for the same sensor may appear (low signal, high signal or intermittent).

Likely causes of the P0112 code

  1. Signal wire shorted to ground by rubbing against the engine or chassis, very common where the harness passes near metal brackets.
  2. Sensor shorted internally, with its resistance dropping to nearly zero ohms.
  3. Connector with water or corrosion that creates a path between pins.
  4. Complementary check: a dirty MAF or a bad air filter will not set this code, but they are worth inspecting because on many models they share the connector.

How to diagnose the P0112 code step by step

  1. Read the sensor live data and compare it with what is expected. With a cold engine after several hours parked, the IAT should match the ambient temperature and agree with the coolant (ECT) sensor within a few degrees.
  2. Inspect the connector. Unplug it, look for green, backed-out or oily pins, and plug it back in firmly.
  3. With the key on and the sensor unplugged, measure the reference at the connector. There should be about 5 V between the signal and ground.
  4. Jumper test. With the sensor unplugged, the scan tool should show about -40 °C (-40 °F). When you join the two connector pins with a wire, it should jump to more than 120 °C (248 °F). If it does, the wiring is fine and the problem is the sensor.
  5. Measure the sensor resistance and compare it with the technical data table at the current temperature.
  6. Do the wiggle test with the engine running. Move the harness and the connector while you watch the live data, because a jump shows you where the fault is.
  7. Check the continuity of each wire between the sensor connector and the computer connector with the key off.

How to fix the P0112 code

  • Find where the wire is rubbing against ground and repair the insulation.
  • If the code changes to high signal when you unplug the sensor, the sensor is shorted, so replace it.
  • Dry and clean the connector if it had water in it.
  • Use a quality original or equivalent sensor, because cheap generic ones often have different response curves.
  • Clear the codes, drive one full cycle and check in live data that the reading makes sense.

Technical reference data

  • Approximate resistance: about 3,500 ohms at 0 °C (32 °F), 2,000 to 2,500 ohms at 20 °C (68 °F) and about 300 ohms at 80 °C (176 °F).
  • Approximate signal voltage: 3 to 3.5 V with air at 20 °C (68 °F), dropping as it warms up.
  • Computer reference: 5 V.
  • Open circuit reading on the scan tool: about -40 °C (-40 °F). Short circuit reading: more than 120 °C (248 °F).
  • Values are approximate, so check the manufacturer data for your engine.

Brand-specific notes

When you see a P0112 code on a turbocharged engine, remember there is usually a second sensor after the intercooler, with its own code.

P0112 on Ford

On many Ford vehicles the IAT is built into the MAF and is not sold separately. If the fault is in the sensor, you replace the whole assembly.

P0112 on GM

On many GM vehicles the IAT is built into the MAF and is not sold separately. If the fault is in the sensor, you replace the whole assembly.

P0112 on Nissan

On many Nissan vehicles the IAT is built into the MAF and is not sold separately. If the fault is in the sensor, you replace the whole assembly.

P0112 on Toyota

On many Toyota vehicles the IAT is built into the MAF and is not sold separately. If the fault is in the sensor, you replace the whole assembly.

Frequently asked questions about P0112

Can I drive with a P0112 code?
Yes. In general there is no immediate risk, but the engine runs on a substitute value and may use more fuel. Get it repaired soon.
Does the P0112 code always mean replacing the IAT sensor?
No. In most cases the fault is in the connector or the wiring. Do the power, ground and continuity tests first.
What is the difference between low signal and high signal?
On a thermistor, a low signal means an impossibly high temperature (a short circuit) and a high signal means an impossibly low temperature (an open circuit).
How much does it cost to fix P0112?
Roughly $15 to $150. The cheapest repair is fixing a connector and the most expensive is replacing the sensor with labor. It varies by shop and region.
What does the P0112 code mean?
It is a generic OBD2 code that means the intake air temperature sensor signal is too low. The computer reads an impossibly high temperature, which usually points to a short to ground.
What is the most common cause of P0112?
A signal wire rubbing against the engine or chassis and shorting to ground. A sensor shorted inside or a connector with water in it come next.

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