P1112
SubaruIntake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage
Medium SeverityThis code indicates that the vehicle's computer is receiving an intermittently low voltage signal from the Intake Air Temperature (IAT) Sensor, suggesting a potential fault in the sensor or its circuit. This can lead to incorrect fuel mixture calculations by the Engine Control Unit (ECU), affecting engine performance and fuel economy.
⚠️ Before You Begin (Safety First)
Always allow the engine to cool before working on any components. Disconnect the battery before performing any electrical diagnostics or repairs to prevent accidental shorts or injury.
Common Symptoms
- Check Engine Light (CEL) illuminated
- Rough idle or poor engine performance
- Decreased fuel economy
- Engine hesitation during acceleration
- Difficulty starting in cold weather
Common Causes
- Faulty or failing Intake Air Temperature (IAT) Sensor
- Corroded or loose electrical connections at the IAT sensor or harness
- Damaged, frayed, or shorted wiring in the IAT sensor circuit
- Engine Control Unit (ECU) fault (less common)
Frequently reported on: Subaru Forester 2008-2015, Subaru Impreza 2006-2011, Subaru Outback 2005-2010, Subaru Legacy 2005-2009
Diagnostic Steps
- Locate the Intake Air Temperature (IAT) Sensor, often found in the air intake duct or manifold.
- Visually inspect the IAT sensor and its electrical connector for any signs of damage, corrosion, or loose connections.
- Carefully disconnect the electrical connector from the IAT sensor.
- Inspect the pins inside the connector for corrosion or bending. Clean with electrical contact cleaner if necessary.
- Using a multimeter, test the resistance of the IAT sensor. Compare readings to your vehicle's service manual specifications (resistance typically changes with temperature).
- Inspect the wiring harness leading to the IAT sensor for any visible signs of damage, fraying, or short circuits.
- If the sensor tests faulty or the wiring is damaged, replace the IAT sensor or repair the wiring.
- Clear the P1112 code using an OBD-II scanner and retest the vehicle.
👨🔧 When to Call a Professional
If after inspecting the Intake Air Temperature (IAT) Sensor and its wiring, the issue persists or if you lack specialized diagnostic tools to test voltage and resistance, it is best to consult a professional mechanic. Intermittent electrical issues can be challenging to diagnose without proper equipment.
Commonly Asked Questions
What does the Intake Air Temperature (IAT) sensor do?
The IAT sensor measures the temperature of the air entering the engine. This information is crucial for the ECU to calculate the correct fuel injection timing and quantity for optimal combustion.
Can I drive with a P1112 code?
While it might not immediately strand you, driving with a P1112 code can lead to reduced fuel economy, poor engine performance, and potentially increased emissions. It's best to address it promptly to prevent further issues.
How can I test the IAT sensor at home?
You can test the IAT sensor using a multimeter to measure its resistance. The resistance should change predictably with temperature; a common test involves comparing readings at room temperature and after warming the sensor slightly with a hairdryer.
Is the IAT sensor expensive to replace?
The IAT sensor itself is typically an inexpensive part, often costing between $20-$60. Replacement is usually straightforward and can be a DIY task.