P0112 — Intake Air Temperature Sensor 1 Circuit Low #

Note: The description of this code may vary depending on your vehicle’s manufacturer.

• Intake Air Temperature Sensor 1 Circuit Low (General/Standard OBD-II)
• Intake Air Temperature Sensor Circuit Low Voltage (Ford, GM)
• Intake Air Temp Sensor 1 Low Input (Toyota, Honda)
• Intake Air Temperature Circuit Low Input (Chrysler, Dodge)

Summary of Code P0112 #

P0112 indicates that the engine control module (ECM) or powertrain control module (PCM) has detected a voltage from the intake air temperature (IAT) sensor 1 that is below the expected range. The IAT sensor measures the temperature of the air entering the engine; this data helps the ECM adjust fuel delivery and ignition timing for optimal performance. A low circuit voltage usually means the sensor is reporting an unusually cold air temperature, which may not reflect reality. This code is common across most OBD-II vehicles, and although not usually critical, it can impact fuel efficiency and engine performance if left unresolved. The root cause is often a sensor wiring problem, a faulty sensor, or sometimes an issue with the ECM itself.

Frequent Symptoms for Code P0112 #

A P0112 code typically triggers a check engine light, but it can also cause noticeable changes in engine behavior. Since the ECM relies on accurate air temperature data to optimize fuel mixture, an incorrect reading can lead to a range of drivability issues. Common symptoms include:

• Illuminated check engine light
• Poor fuel economy
• Rough idle
• Hard starting, especially in cold weather
• Reduced engine power or sluggish acceleration
• Increased exhaust emissions

Probable Causes for Code P0112 #

Most cases of code P0112 trace back to issues in the IAT sensor circuit. The sensor itself is a thermistor, meaning its resistance changes with temperature. When the circuit signal is too low, the ECM interprets this as extremely cold intake air. Here are the most common causes, listed by frequency:

1. Faulty or damaged IAT sensor
2. Short to ground in the IAT sensor wiring
3. Corroded, loose, or disconnected IAT sensor connector
4. Damaged wiring harness (especially from rodent damage or abrasion)
5. Faulty ECM/PCM (rare)

Step-by-Step Diagnostic for Code P0112 #

Proper diagnosis ensures you address the real issue, not just the symptom. Here’s a structured approach to safely and efficiently diagnose P0112:

• Confirm the code using a reliable OBD-II scanner. Note any additional codes that may affect diagnosis.
• Visually inspect the IAT sensor and its wiring near the intake air duct or manifold. Look for obvious signs of damage, corrosion, or disconnection.
• Check the sensor connector for bent pins, corrosion, or loose fit.
• Test the IAT sensor resistance with a multimeter. Compare readings to OEM specifications at room temperature and with heat applied (using a hairdryer, for example).
• Check for short circuits by measuring voltage at the connector with the key on. Verify that the reference voltage matches OEM specs (usually around 5V).
• Inspect the wiring harness along its length for breaks, pinches, or rodent damage.
• If all else checks out, test the circuit from the sensor to the ECM for continuity and shorts.
• Consider ECM/PCM testing or replacement only after all other possibilities are ruled out.

Possible Repairs for Code P0112 #

Once the underlying issue is identified, repairs are typically straightforward and cost-effective. Here’s what is usually required:

• Replace the IAT sensor if it fails resistance, voltage, or visual tests.
• Repair or replace damaged wiring in the sensor circuit.
• Clean or replace the sensor connector if corroded or loose.
• Secure any loose connections to ensure consistent sensor readings.
• Replace or repair the ECM/PCM only if confirmed faulty after all other steps.

Can You Drive with Code P0112? #

Yes, but with caution. A vehicle with code P0112 is usually drivable, as the engine will default to a safe fuel map. However, prolonged driving with this code can lead to poor fuel economy, reduced performance, and potential long-term engine wear. If you notice severe drivability issues or poor starting, it’s best to address the problem promptly to avoid further complications.

Vehicles Most Commonly Affected by Code P0112 #

P0112 appears across a wide range of OBD-II compliant vehicles, but is especially common in certain makes and models due to sensor placement and wiring design. The following vehicles are often reported with this code:

• Ford F-Series (F-150, F-250, etc.)
• Chevrolet Silverado and GMC Sierra
• Toyota Camry and Corolla
• Honda Accord and Civic
• Dodge Ram 1500
• Nissan Altima
• Volkswagen Jetta and Golf

Common Mistakes & Best Practices for Code P0112 #

It’s easy to misdiagnose P0112, especially if you skip steps or rely solely on code readers. Avoid these pitfalls and follow these tips:

• Do not replace the sensor without checking wiring and connectors first. Many times, the issue is a simple wiring fault.
• Do not clear the code before verifying repairs. Ensure the code does not return after test driving.
• Always use OEM or high-quality replacement parts. Cheap or incompatible sensors can cause recurring issues.
• Double-check for related codes. Sometimes, multiple codes can point to a common underlying problem.

Quick FAQ for Code P0112 #

Here are answers to the most common questions about this code:

• Can a dirty air filter trigger P0112?
  No, a dirty air filter may reduce engine performance, but it does not directly affect the IAT sensor circuit voltage.
• Is it expensive to fix P0112?
  Most repairs involve simple sensor or wiring replacement, which are generally affordable. ECM/PCM repairs are rare and more costly.
• Can I reset the code with a scanner and forget about it?
  You can clear the code, but if the underlying issue persists, the code will return. Always diagnose and repair the root cause.