P0112 – Intake Air Temperature Circuit Low Input

The P0112 code indicates that the intake air temperature (IAT) sensor circuit is reporting a voltage below the normal operating range. This code is fairly urgent, as driving with a faulty IAT sensor can lead to poor engine performance, reduced fuel efficiency, and potential engine damage. While it may be possible to continue driving for a short distance, it's best to diagnose and fix the issue as soon as possible.

What is the P0112 Code?

The P0112 code is a generic powertrain code that applies to most makes and models of vehicles. It indicates that the voltage being reported by the IAT sensor circuit is below the expected range, typically less than 0.2 volts.

The IAT sensor, also known as the air charge temperature sensor or manifold air temperature sensor, measures the temperature of the air entering the engine. The engine control module (ECM) uses this information to adjust the air-fuel mixture and ignition timing for optimal performance.

Parts Involved

The main components involved with the P0112 code are:

• Intake Air Temperature Sensor: Located in the intake manifold or air cleaner assembly. Measures air temperature using a thermistor.
• Wiring and Connectors: Carries the IAT sensor signal to the ECM. Damage or corrosion can cause the low voltage condition.
• Engine Control Module: Receives input from the IAT sensor and controls engine parameters. A faulty ECM could misinterpret the sensor signal.

Common Causes

Some of the most common causes of a P0112 code include:

1. Faulty IAT sensor (most common)
2. Damaged wiring or connectors
3. Intake air leak
4. Faulty ECM (rare)

Diagnosing the P0112 Code

To properly diagnose a P0112 code, follow these steps:

1. Check for related codes. Other codes like P0113 (high input) or P0111 (intermittent) can help narrow down the issue.

2. Visually inspect the IAT sensor, wiring, and connectors. Look for damage, corrosion, or loose connections. Repair or replace as needed.

3. Test the IAT sensor resistance. At room temperature (20°C/68°F), the sensor should read around 2,000-3,000 ohms. At 0°C (32°F), it should read 7,000-10,000 ohms.

4. Check for intake air leaks. A vacuum leak can allow unmetered air into the engine, causing the low voltage reading. Repair any leaks found.

5. Verify ECM operation. If all other components check out, the ECM may be at fault. This will require professional diagnosis.

Repair Solutions and Costs

In most cases, the solution for a P0112 code will be to replace the IAT sensor. The cost for the sensor itself is typically around $20-$120 USD (€18-€108 EUR). Labor costs will vary, but expect to pay $50-$150 USD (€45-€135 EUR) for professional installation.

If wiring or intake leaks are found, repair costs will depend on the extent of the damage. An ECM replacement is rare but would be much more expensive, potentially exceeding $1,000 USD (€900 EUR).

Prevention and Related Issues

To prevent IAT sensor issues, regularly inspect the air intake system for leaks or damage. Avoid using low-quality air filters that may allow debris into the sensor.

Other common fault codes that may appear alongside P0112 include:

• P0113 – IAT Sensor Circuit High Input
• P0111 – IAT Sensor Circuit Intermittent
• P0171/P0174 – Fuel System Too Lean

Frequently Asked Questions About P0112 Engine Code

What does the P0112 code mean?

P0112 is a generic OBD-II code that stands for “Intake Air Temperature Sensor 1 Circuit Low”. It indicates that the engine control module (ECM) has detected a low voltage reading from the intake air temperature (IAT) sensor.

How urgent is it to fix a P0112 code?

While you may be able to drive short distances with a P0112 code, it’s best to diagnose and fix the issue as soon as possible to prevent poor engine performance, reduced fuel efficiency, and potential engine damage.

What are the common symptoms of a P0112 code?

Common symptoms include:

• Check engine light illuminated
• Hard starting
• Rough running or misfiring
• Hesitation or lack of power during acceleration
• Poor fuel economy

What are the most likely causes of a P0112 code?

The most common causes are:

• Faulty IAT sensor
• Damaged wiring or loose/corroded connectors to the IAT sensor
• Intake air leaks
• Dirty or clogged air filter

Where is the intake air temperature sensor located?

The IAT sensor is typically located in the intake manifold or air cleaner assembly. It may be integrated with the mass airflow (MAF) sensor in some vehicles.

How does the IAT sensor work?

The IAT sensor contains a thermistor that changes resistance based on air temperature. As temperature increases, the resistance decreases, varying the voltage signal sent to the ECM. The ECM uses this to adjust the air-fuel mixture.

Can I drive with a P0112 code?

It’s not advisable to drive extensively with a P0112 code. While the vehicle may run, you risk poor performance and fuel economy. Ignoring the code for too long could lead to catalytic converter or engine damage.

How do you diagnose a P0112 code?

Diagnosis steps include:

1. Check for related trouble codes.
2. Visually inspect the IAT sensor, wiring, and connectors.
3. Test the IAT sensor resistance with an ohmmeter.
4. Check for intake air leaks.
5. Verify the ECM is functioning properly.

What should the IAT sensor resistance be?

At 68°F (20°C), the IAT sensor resistance should be approximately 2,000-3,000 ohms. At 32°F (0°C), it should read around 7,000-10,000 ohms. Always refer to manufacturer specifications for exact values.

How much does it cost to fix a P0112 code?

If you need to replace the IAT sensor, expect to pay around $20-$120 for the part and $50-$150 for labor, depending on the vehicle. Costs will be higher if there is wiring damage or other repairs needed.

Can a dirty air filter cause a P0112 code?

Yes, a dirty or clogged air filter can restrict airflow, causing incorrect temperature readings. Always check and replace the air filter if needed when diagnosing a P0112.

Can I replace the IAT sensor myself?

Replacing the IAT sensor is often a straightforward job that most DIYers can do with basic tools. However, always consult a repair manual for your specific vehicle to ensure proper procedures are followed.

What other codes may appear with a P0112?

Related codes that may appear alongside a P0112 include:

• P0113 (IAT Sensor Circuit High)
• P0111 (IAT Sensor Performance)
• P0171/P0174 (Fuel System Too Lean)
• MAF sensor codes like P0101 or P0102

How do I clear a P0112 code after repairs?

After repairs, you can clear the code by:

1. Disconnecting the battery for a few minutes.
2. Using an OBD-II scanner to erase the codes.
3. Allowing the code to self-clear after several drive cycles if the issue is fixed.

Will a P0112 code cause a vehicle to fail an emissions test?

Yes, a P0112 code will likely cause your vehicle to fail an emissions or smog test. The check engine light will be illuminated, and the IAT sensor malfunction can cause increased emissions.

What happens if I ignore a P0112 code?

Ignoring a P0112 code can result in:

• Progressively worse engine performance
• Reduced fuel economy
• Rough running and misfires
• Damage to spark plugs, O2 sensors, or catalytic converter
• Internal engine damage if left unaddressed for too long

Can a P0112 code be caused by an intake air leak?

Yes, an intake air leak can allow unmetered air to enter the engine, causing an incorrect low temperature reading from the IAT sensor. Inspect the intake tract for cracks, loose clamps, or damaged hoses.

How often should I replace the IAT sensor?

There is no standard service interval for the IAT sensor. They typically last the lifetime of the vehicle but can fail prematurely due to damage, corrosion, or contamination. Replace if testing indicates a malfunction.

Can a malfunctioning IAT sensor damage the engine?

Indirectly, yes. A faulty IAT sensor can cause incorrect air-fuel ratios, leading to misfires, increased emissions, and catalytic converter damage. Severe cases of unaddressed lean conditions can cause engine overheating and internal damage.

What is the difference between an IAT sensor and a MAF sensor?

While both sensors deal with intake air, the IAT measures air temperature while the MAF measures airflow volume. Some vehicles integrate both sensors into one unit. A P0112 code relates specifically to the temperature reading function.